diff --git a/backend/app/auth.py b/backend/app/auth.py
index 129d3f4..945bc84 100644
--- a/backend/app/auth.py
+++ b/backend/app/auth.py
@@ -1,13 +1,15 @@
 from datetime import datetime, timezone
-from typing import Dict, Any, Optional
+from typing import Any, Dict, Optional
 
-from fastapi import Depends, HTTPException, status, Request
+from fastapi import Depends, HTTPException, Request, Response, status
 from fastapi.security import OAuth2PasswordBearer
 
+from .config import settings
 from .db import get_user_by_username, set_user_auth_provider, upsert_user_activity
-from .security import safe_decode_token, TokenError, verify_password
+from .network_security import request_trusts_forwarded_headers
+from .security import TokenError, safe_decode_token, verify_password
 
-oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/auth/login")
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/auth/login", auto_error=False)
 
 
 def _is_expired(expires_at: str | None) -> bool:
@@ -24,20 +26,79 @@ def _is_expired(expires_at: str | None) -> bool:
         parsed = parsed.replace(tzinfo=timezone.utc)
     return parsed <= datetime.now(timezone.utc)
 
+
 def _extract_client_ip(request: Request) -> str:
-    forwarded = request.headers.get("x-forwarded-for")
-    if forwarded:
-        parts = [part.strip() for part in forwarded.split(",") if part.strip()]
-        if parts:
-            return parts[0]
-    real_ip = request.headers.get("x-real-ip")
-    if real_ip:
-        return real_ip.strip()
-    if request.client and request.client.host:
-        return request.client.host
+    direct_host = request.client.host if request.client else None
+    if request_trusts_forwarded_headers(direct_host):
+        forwarded = request.headers.get("x-forwarded-for")
+        if forwarded:
+            parts = [part.strip() for part in forwarded.split(",") if part.strip()]
+            if parts:
+                return parts[0]
+        real_ip = request.headers.get("x-real-ip")
+        if real_ip:
+            return real_ip.strip()
+    if direct_host:
+        return direct_host
     return "unknown"
 
 
+def _cookie_settings() -> dict[str, Any]:
+    samesite = str(settings.auth_cookie_samesite or "lax").strip().lower()
+    if samesite not in {"lax", "strict", "none"}:
+        samesite = "lax"
+    return {
+        "secure": bool(settings.auth_cookie_secure),
+        "httponly": True,
+        "samesite": samesite,
+        "domain": settings.auth_cookie_domain or None,
+        "path": "/",
+    }
+
+
+def _state_cookie_settings() -> dict[str, Any]:
+    cookie = _cookie_settings()
+    cookie["httponly"] = False
+    return cookie
+
+
+def set_auth_cookies(response: Response, token: str) -> None:
+    max_age = max(60, int(settings.jwt_exp_minutes or 720) * 60)
+    response.set_cookie(
+        settings.auth_cookie_name,
+        token,
+        max_age=max_age,
+        **_cookie_settings(),
+    )
+    response.set_cookie(
+        settings.auth_state_cookie_name,
+        "1",
+        max_age=max_age,
+        **_state_cookie_settings(),
+    )
+
+
+def clear_auth_cookies(response: Response) -> None:
+    response.delete_cookie(settings.auth_cookie_name, path="/", domain=settings.auth_cookie_domain or None)
+    response.delete_cookie(
+        settings.auth_state_cookie_name,
+        path="/",
+        domain=settings.auth_cookie_domain or None,
+    )
+
+
+def _extract_access_token(request: Request, oauth_token: Optional[str]) -> Optional[str]:
+    auth_header = request.headers.get("authorization", "")
+    if auth_header.lower().startswith("bearer "):
+        return auth_header.split(" ", 1)[1].strip()
+    if oauth_token:
+        return oauth_token
+    cookie_token = request.cookies.get(settings.auth_cookie_name)
+    if isinstance(cookie_token, str) and cookie_token.strip():
+        return cookie_token.strip()
+    return None
+
+
 def resolve_user_auth_provider(user: Optional[Dict[str, Any]]) -> str:
     if not isinstance(user, dict):
         return "local"
@@ -122,24 +183,28 @@ def _load_current_user_from_token(
     }
 
 
-def get_current_user(token: str = Depends(oauth2_scheme), request: Request = None) -> Dict[str, Any]:
-    return _load_current_user_from_token(token, request)
-
-
-def get_current_user_event_stream(request: Request) -> Dict[str, Any]:
-    """EventSource cannot send Authorization headers, so allow a short-lived stream token via query."""
-    token = None
-    stream_query_token = None
-    auth_header = request.headers.get("authorization", "")
-    if auth_header.lower().startswith("bearer "):
-        token = auth_header.split(" ", 1)[1].strip()
-    if not token:
-        stream_query_token = request.query_params.get("stream_token")
-    if not token and not stream_query_token:
+def get_current_user(
+    request: Request,
+    token: Optional[str] = Depends(oauth2_scheme),
+) -> Dict[str, Any]:
+    resolved_token = _extract_access_token(request, token)
+    if not resolved_token:
+        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Missing token")
+    return _load_current_user_from_token(resolved_token, request)
+
+
+def get_current_user_event_stream(
+    request: Request,
+    token: Optional[str] = Depends(oauth2_scheme),
+) -> Dict[str, Any]:
+    """EventSource cannot send Authorization headers, so allow a short-lived stream token via query."""
+    resolved_token = _extract_access_token(request, token)
+    stream_query_token = request.query_params.get("stream_token")
+    if resolved_token:
+        # Allow standard bearer tokens for non-browser EventSource clients.
+        return _load_current_user_from_token(resolved_token, None)
+    if not stream_query_token:
         raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Missing token")
-    if token:
-        # Allow standard bearer tokens in Authorization for non-browser EventSource clients.
-        return _load_current_user_from_token(token, None)
     return _load_current_user_from_token(
         str(stream_query_token),
         None,
diff --git a/backend/app/config.py b/backend/app/config.py
index 65a42e6..ddea219 100644
--- a/backend/app/config.py
+++ b/backend/app/config.py
@@ -12,7 +12,7 @@ class Settings(BaseSettings):
     sqlite_journal_mode: str = Field(
         default="DELETE", validation_alias=AliasChoices("SQLITE_JOURNAL_MODE")
     )
-    jwt_secret: str = Field(default="change-me", validation_alias=AliasChoices("JWT_SECRET"))
+    jwt_secret: str = Field(default="", validation_alias=AliasChoices("JWT_SECRET"))
     jwt_exp_minutes: int = Field(default=720, validation_alias=AliasChoices("JWT_EXP_MINUTES"))
     api_docs_enabled: bool = Field(default=False, validation_alias=AliasChoices("API_DOCS_ENABLED"))
     auth_rate_limit_window_seconds: int = Field(
@@ -34,7 +34,22 @@ class Settings(BaseSettings):
         default=3, validation_alias=AliasChoices("PASSWORD_RESET_RATE_LIMIT_MAX_ATTEMPTS_IDENTIFIER")
     )
     admin_username: str = Field(default="admin", validation_alias=AliasChoices("ADMIN_USERNAME"))
-    admin_password: str = Field(default="adminadmin", validation_alias=AliasChoices("ADMIN_PASSWORD"))
+    admin_password: str = Field(default="", validation_alias=AliasChoices("ADMIN_PASSWORD"))
+    auth_cookie_name: str = Field(
+        default="magent_auth", validation_alias=AliasChoices("AUTH_COOKIE_NAME")
+    )
+    auth_cookie_secure: bool = Field(
+        default=False, validation_alias=AliasChoices("AUTH_COOKIE_SECURE")
+    )
+    auth_cookie_samesite: str = Field(
+        default="lax", validation_alias=AliasChoices("AUTH_COOKIE_SAMESITE")
+    )
+    auth_cookie_domain: Optional[str] = Field(
+        default=None, validation_alias=AliasChoices("AUTH_COOKIE_DOMAIN")
+    )
+    auth_state_cookie_name: str = Field(
+        default="magent_logged_in", validation_alias=AliasChoices("AUTH_STATE_COOKIE_NAME")
+    )
     log_level: str = Field(default="INFO", validation_alias=AliasChoices("LOG_LEVEL"))
     log_file: str = Field(default="data/magent.log", validation_alias=AliasChoices("LOG_FILE"))
     log_file_max_bytes: int = Field(
@@ -121,6 +136,10 @@ class Settings(BaseSettings):
     magent_proxy_trust_forwarded_headers: bool = Field(
         default=True, validation_alias=AliasChoices("MAGENT_PROXY_TRUST_FORWARDED_HEADERS")
     )
+    magent_proxy_trusted_proxies: str = Field(
+        default="127.0.0.1,::1",
+        validation_alias=AliasChoices("MAGENT_PROXY_TRUSTED_PROXIES"),
+    )
     magent_proxy_forwarded_prefix: Optional[str] = Field(
         default=None, validation_alias=AliasChoices("MAGENT_PROXY_FORWARDED_PREFIX")
     )
@@ -216,6 +235,10 @@ class Settings(BaseSettings):
     magent_notify_webhook_url: Optional[str] = Field(
         default=None, validation_alias=AliasChoices("MAGENT_NOTIFY_WEBHOOK_URL")
     )
+    magent_allow_private_notification_targets: bool = Field(
+        default=False,
+        validation_alias=AliasChoices("MAGENT_ALLOW_PRIVATE_NOTIFICATION_TARGETS"),
+    )
 
     jellyseerr_base_url: Optional[str] = Field(
         default=None, validation_alias=AliasChoices("JELLYSEERR_URL", "JELLYSEERR_BASE_URL")
@@ -288,7 +311,7 @@ class Settings(BaseSettings):
     )
 
     discord_webhook_url: Optional[str] = Field(
-        default="https://discord.com/api/webhooks/1464141924775629033/O_rvCAmIKowR04tyAN54IuMPcQFEiT-ustU3udDaMTlF62PmoI6w4-52H3ZQcjgHQOgt",
+        default=None,
         validation_alias=AliasChoices("DISCORD_WEBHOOK_URL"),
     )
 
diff --git a/backend/app/db.py b/backend/app/db.py
index 2bc3892..9d2c156 100644
--- a/backend/app/db.py
+++ b/backend/app/db.py
@@ -21,6 +21,8 @@ SQLITE_BUSY_TIMEOUT_MS = 5_000
 SQLITE_CACHE_SIZE_KIB = 32_768
 SQLITE_MMAP_SIZE_BYTES = 256 * 1024 * 1024
 _DB_UNSET = object()
+_DEFAULT_JWT_SECRET = "change-me"
+_DEFAULT_ADMIN_PASSWORD = "adminadmin"
 
 
 def _db_path() -> str:
@@ -178,6 +180,11 @@ def _normalize_stored_email(value: Optional[Any]) -> Optional[str]:
     return candidate
 
 
+def _has_secure_bootstrap_admin_credentials() -> bool:
+    password = str(settings.admin_password or "")
+    return bool(password and password != _DEFAULT_ADMIN_PASSWORD)
+
+
 def init_db() -> None:
     with _connect() as conn:
         conn.execute(
@@ -767,7 +774,7 @@ def get_recent_actions(request_id: str, limit: int = 10) -> list[dict[str, Any]]
 
 
 def ensure_admin_user() -> None:
-    if not settings.admin_username or not settings.admin_password:
+    if not settings.admin_username or not _has_secure_bootstrap_admin_credentials():
         return
     existing = get_user_by_username(settings.admin_username)
     if existing:
@@ -775,6 +782,14 @@ def ensure_admin_user() -> None:
     create_user(settings.admin_username, settings.admin_password, role="admin")
 
 
+def has_admin_user() -> bool:
+    with _connect() as conn:
+        row = conn.execute(
+            "SELECT 1 FROM users WHERE LOWER(role) = 'admin' LIMIT 1"
+        ).fetchone()
+    return bool(row)
+
+
 def create_user(
     username: str,
     password: str,
diff --git a/backend/app/main.py b/backend/app/main.py
index a07105e..5db75d8 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -8,7 +8,7 @@ from fastapi import FastAPI, Request
 from fastapi.middleware.cors import CORSMiddleware
 
 from .config import settings
-from .db import init_db
+from .db import has_admin_user, init_db
 from .routers.requests import (
     router as requests_router,
     startup_warmup_requests_cache,
@@ -165,13 +165,15 @@ def _launch_background_task(name: str, coroutine_factory: Callable[[], Awaitable
 
 
 def _log_security_configuration_warnings() -> None:
-    if str(settings.jwt_secret or "").strip() == "change-me":
+    jwt_secret = str(settings.jwt_secret or "").strip()
+    if not jwt_secret or jwt_secret == "change-me":
         logger.warning(
-            "security configuration warning: JWT_SECRET is still set to the default value"
+            "security configuration warning: JWT_SECRET is unset or still set to the default value"
         )
-    if str(settings.admin_password or "") == "adminadmin":
+    admin_password = str(settings.admin_password or "")
+    if not admin_password or admin_password == "adminadmin":
         logger.warning(
-            "security configuration warning: ADMIN_PASSWORD is still set to the bootstrap default"
+            "security configuration warning: ADMIN_PASSWORD is unset or still set to the bootstrap default"
         )
     if bool(settings.api_docs_enabled):
         logger.warning(
@@ -179,6 +181,17 @@ def _log_security_configuration_warnings() -> None:
         )
 
 
+def _enforce_secure_startup_configuration() -> None:
+    jwt_secret = str(settings.jwt_secret or "").strip()
+    if not jwt_secret or jwt_secret == "change-me":
+        raise RuntimeError("JWT_SECRET must be set to a strong, non-default value before startup.")
+    admin_password = str(settings.admin_password or "")
+    if not has_admin_user() and (not admin_password or admin_password == "adminadmin"):
+        raise RuntimeError(
+            "A secure ADMIN_PASSWORD is required on first startup until an admin account exists."
+        )
+
+
 @app.on_event("startup")
 async def startup() -> None:
     configure_logging(
@@ -192,6 +205,7 @@ async def startup() -> None:
     logger.info("startup begin app=%s build=%s", settings.app_name, settings.site_build_number)
     _log_security_configuration_warnings()
     init_db()
+    _enforce_secure_startup_configuration()
     runtime = get_runtime_settings()
     configure_logging(
         runtime.log_level,
diff --git a/backend/app/network_security.py b/backend/app/network_security.py
new file mode 100644
index 0000000..68219ed
--- /dev/null
+++ b/backend/app/network_security.py
@@ -0,0 +1,132 @@
+from __future__ import annotations
+
+import ipaddress
+import socket
+from functools import lru_cache
+from typing import Iterable
+from urllib.parse import urlparse
+
+from .config import settings
+
+_METADATA_HOSTS = {
+    "169.254.169.254",
+    "metadata.google.internal",
+    "metadata.azure.internal",
+}
+
+
+def _normalize_text(value: object) -> str:
+    if value is None:
+        return ""
+    return str(value).strip()
+
+
+def _split_csv(value: object) -> list[str]:
+    raw = _normalize_text(value)
+    if not raw:
+        return []
+    return [part.strip() for part in raw.split(",") if part.strip()]
+
+
+def _ip_is_sensitive(ip_obj: ipaddress._BaseAddress) -> bool:
+    return bool(
+        ip_obj.is_loopback
+        or ip_obj.is_link_local
+        or ip_obj.is_multicast
+        or ip_obj.is_unspecified
+        or ip_obj.is_reserved
+        or ip_obj.is_private
+    )
+
+
+@lru_cache(maxsize=256)
+def _resolve_host_ips(host: str) -> tuple[ipaddress._BaseAddress, ...]:
+    resolved: list[ipaddress._BaseAddress] = []
+    for family, _, _, _, sockaddr in socket.getaddrinfo(host, None):
+        if family == socket.AF_INET:
+            resolved.append(ipaddress.ip_address(sockaddr[0]))
+        elif family == socket.AF_INET6:
+            resolved.append(ipaddress.ip_address(sockaddr[0]))
+    return tuple(resolved)
+
+
+def _is_trusted_proxy_host(host: str, trusted_proxies: Iterable[str]) -> bool:
+    candidate = _normalize_text(host)
+    if not candidate:
+        return False
+    try:
+        host_ip = ipaddress.ip_address(candidate)
+    except ValueError:
+        return candidate.lower() in {entry.lower() for entry in trusted_proxies}
+
+    for entry in trusted_proxies:
+        raw = _normalize_text(entry)
+        if not raw:
+            continue
+        try:
+            if "/" in raw:
+                if host_ip in ipaddress.ip_network(raw, strict=False):
+                    return True
+            elif host_ip == ipaddress.ip_address(raw):
+                return True
+        except ValueError:
+            continue
+    return False
+
+
+def request_trusts_forwarded_headers(client_host: str | None) -> bool:
+    if not settings.magent_proxy_enabled or not settings.magent_proxy_trust_forwarded_headers:
+        return False
+    trusted = _split_csv(settings.magent_proxy_trusted_proxies)
+    if not trusted:
+        return False
+    return _is_trusted_proxy_host(client_host or "", trusted)
+
+
+def validate_notification_target_url(
+    url: str,
+    *,
+    allow_private: bool | None = None,
+) -> str:
+    raw = _normalize_text(url)
+    if not raw:
+        raise ValueError("URL cannot be empty.")
+
+    parsed = urlparse(raw)
+    if parsed.scheme not in {"http", "https"}:
+        raise ValueError("URL must use http:// or https://.")
+    if parsed.username or parsed.password:
+        raise ValueError("URL must not embed credentials.")
+    hostname = _normalize_text(parsed.hostname).lower()
+    if not hostname:
+        raise ValueError("URL must include a valid host.")
+
+    allow_private_targets = (
+        settings.magent_allow_private_notification_targets
+        if allow_private is None
+        else bool(allow_private)
+    )
+    if hostname in _METADATA_HOSTS:
+        raise ValueError("Metadata service targets are not allowed.")
+    if hostname == "localhost" and not allow_private_targets:
+        raise ValueError("Local notification targets are not allowed.")
+
+    try:
+        host_ip = ipaddress.ip_address(hostname)
+    except ValueError:
+        host_ip = None
+
+    if host_ip is not None:
+        if _ip_is_sensitive(host_ip) and not allow_private_targets:
+            raise ValueError("Private or local notification targets are not allowed.")
+        return raw
+
+    try:
+        resolved_ips = _resolve_host_ips(hostname)
+    except socket.gaierror as exc:
+        raise ValueError("Host could not be resolved.") from exc
+    if not resolved_ips:
+        raise ValueError("Host could not be resolved.")
+    if not allow_private_targets and any(_ip_is_sensitive(ip_obj) for ip_obj in resolved_ips):
+        raise ValueError("Private or local notification targets are not allowed.")
+    return raw
diff --git a/backend/app/routers/admin.py b/backend/app/routers/admin.py
index 3d1844a..232351a 100644
--- a/backend/app/routers/admin.py
+++ b/backend/app/routers/admin.py
@@ -20,6 +20,7 @@ from ..auth import (
     resolve_user_auth_provider,
 )
 from ..config import settings as env_settings
+from ..network_security import validate_notification_target_url
 from ..db import (
     delete_setting,
     get_all_users,
@@ -153,6 +154,12 @@ URL_SETTING_KEYS = {
     "qbittorrent_base_url",
 }
 
+NOTIFICATION_URL_SETTING_KEYS = {
+    "magent_notify_discord_webhook_url",
+    "magent_notify_push_base_url",
+    "magent_notify_webhook_url",
+}
+
 SETTING_KEYS: List[str] = [
     "magent_application_url",
     "magent_application_port",
@@ -659,6 +666,12 @@ async def update_settings(payload: Dict[str, Any]) -> Dict[str, Any]:
             except ValueError as exc:
                 friendly_key = key.replace("_", " ")
                 raise HTTPException(status_code=400, detail=f"{friendly_key}: {exc}") from exc
+        if key in NOTIFICATION_URL_SETTING_KEYS and value_to_store:
+            try:
+                value_to_store = validate_notification_target_url(value_to_store)
+            except ValueError as exc:
+                friendly_key = key.replace("_", " ")
+                raise HTTPException(status_code=400, detail=f"{friendly_key}: {exc}") from exc
         set_setting(key, value_to_store)
         updates += 1
         changed_keys.append(key)
diff --git a/backend/app/routers/auth.py b/backend/app/routers/auth.py
index 46d93bb..018636e 100644
--- a/backend/app/routers/auth.py
+++ b/backend/app/routers/auth.py
@@ -7,7 +7,7 @@ import time
 from threading import Lock
 
 import httpx
-from fastapi import APIRouter, HTTPException, status, Depends, Request
+from fastapi import APIRouter, HTTPException, status, Depends, Request, Response
 from fastapi.security import OAuth2PasswordRequestForm
 
 from ..db import (
@@ -47,8 +47,15 @@ from ..security import (
     verify_password,
 )
 from ..security import create_stream_token
-from ..auth import get_current_user, normalize_user_auth_provider, resolve_user_auth_provider
+from ..auth import (
+    clear_auth_cookies,
+    get_current_user,
+    normalize_user_auth_provider,
+    resolve_user_auth_provider,
+    set_auth_cookies,
+)
 from ..config import settings
+from ..network_security import request_trusts_forwarded_headers
 from ..services.user_cache import (
     build_jellyseerr_candidate_map,
     extract_jellyseerr_user_email,
@@ -96,12 +103,14 @@ def _require_recipient_email(value: object) -> str:
 
 
 def _auth_client_ip(request: Request) -> str:
-    forwarded = request.headers.get("x-forwarded-for")
-    if isinstance(forwarded, str) and forwarded.strip():
-        return forwarded.split(",", 1)[0].strip()
-    real = request.headers.get("x-real-ip")
-    if isinstance(real, str) and real.strip():
-        return real.strip()
+    direct_host = request.client.host if request.client else None
+    if request_trusts_forwarded_headers(direct_host):
+        forwarded = request.headers.get("x-forwarded-for")
+        if isinstance(forwarded, str) and forwarded.strip():
+            return forwarded.split(",", 1)[0].strip()
+        real = request.headers.get("x-real-ip")
+        if isinstance(real, str) and real.strip():
+            return real.strip()
     if request.client and request.client.host:
         return str(request.client.host)
     return "unknown"
@@ -358,6 +367,15 @@ def _assert_user_can_login(user: dict | None) -> None:
         raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="User access has expired")
 
 
+def _auth_success_response(response: Response, token: str, user_payload: dict) -> dict:
+    set_auth_cookies(response, token)
+    return {
+        "authenticated": True,
+        "token_type": "cookie",
+        "user": user_payload,
+    }
+
+
 def _public_invite_payload(invite: dict, profile: dict | None = None) -> dict:
     return {
         "code": invite.get("code"),
@@ -580,7 +598,11 @@ def _master_invite_controlled_values(master_invite: dict) -> tuple[int | None, s
 
 
 @router.post("/login")
-async def login(request: Request, form_data: OAuth2PasswordRequestForm = Depends()) -> dict:
+async def login(
+    request: Request,
+    response: Response,
+    form_data: OAuth2PasswordRequestForm = Depends(),
+) -> dict:
     _enforce_login_rate_limit(request, form_data.username)
     logger.info(
         "login attempt provider=local username=%s client=%s",
@@ -629,15 +651,19 @@ async def login(request: Request, form_data: OAuth2PasswordRequestForm = Depends
         user["role"],
         _auth_client_ip(request),
     )
-    return {
-        "access_token": token,
-        "token_type": "bearer",
-        "user": {"username": user["username"], "role": user["role"]},
-    }
+    return _auth_success_response(
+        response,
+        token,
+        {"username": user["username"], "role": user["role"]},
+    )
 
 
 @router.post("/jellyfin/login")
-async def jellyfin_login(request: Request, form_data: OAuth2PasswordRequestForm = Depends()) -> dict:
+async def jellyfin_login(
+    request: Request,
+    response: Response,
+    form_data: OAuth2PasswordRequestForm = Depends(),
+) -> dict:
     _enforce_login_rate_limit(request, form_data.username)
     logger.info(
         "login attempt provider=jellyfin username=%s client=%s",
@@ -668,13 +694,13 @@ async def jellyfin_login(request: Request, form_data: OAuth2PasswordRequestForm
             canonical_username,
             _auth_client_ip(request),
         )
-        return {
-            "access_token": token,
-            "token_type": "bearer",
-            "user": {"username": canonical_username, "role": "user"},
-        }
+        return _auth_success_response(
+            response,
+            token,
+            {"username": canonical_username, "role": "user"},
+        )
     try:
-        response = await client.authenticate_by_name(username, password)
+        auth_response = await client.authenticate_by_name(username, password)
     except Exception as exc:
         logger.exception(
             "login upstream error provider=jellyfin username=%s client=%s",
@@ -682,7 +708,7 @@ async def jellyfin_login(request: Request, form_data: OAuth2PasswordRequestForm
             _auth_client_ip(request),
         )
         raise HTTPException(status_code=status.HTTP_502_BAD_GATEWAY, detail=str(exc)) from exc
-    if not isinstance(response, dict) or not response.get("User"):
+    if not isinstance(auth_response, dict) or not auth_response.get("User"):
         _record_login_failure(request, username)
         raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid Jellyfin credentials")
     if not preferred_match:
@@ -724,16 +750,20 @@ async def jellyfin_login(request: Request, form_data: OAuth2PasswordRequestForm
         get_user_by_username(canonical_username).get("jellyseerr_user_id") if get_user_by_username(canonical_username) else None,
         _auth_client_ip(request),
     )
-    return {
-        "access_token": token,
-        "token_type": "bearer",
-        "user": {"username": canonical_username, "role": "user"},
-    }
+    return _auth_success_response(
+        response,
+        token,
+        {"username": canonical_username, "role": "user"},
+    )
 
 
 @router.post("/seerr/login")
 @router.post("/jellyseerr/login")
-async def jellyseerr_login(request: Request, form_data: OAuth2PasswordRequestForm = Depends()) -> dict:
+async def jellyseerr_login(
+    request: Request,
+    response: Response,
+    form_data: OAuth2PasswordRequestForm = Depends(),
+) -> dict:
     _enforce_login_rate_limit(request, form_data.username)
     logger.info(
         "login attempt provider=seerr username=%s client=%s",
@@ -745,7 +775,7 @@ async def jellyseerr_login(request: Request, form_data: OAuth2PasswordRequestFor
     if not client.configured():
         raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Seerr not configured")
     try:
-        response = await client.login_local(form_data.username, form_data.password)
+        auth_response = await client.login_local(form_data.username, form_data.password)
     except Exception as exc:
         logger.exception(
             "login upstream error provider=seerr username=%s client=%s",
@@ -753,11 +783,11 @@ async def jellyseerr_login(request: Request, form_data: OAuth2PasswordRequestFor
             _auth_client_ip(request),
         )
         raise HTTPException(status_code=status.HTTP_502_BAD_GATEWAY, detail=str(exc)) from exc
-    if not isinstance(response, dict):
+    if not isinstance(auth_response, dict):
         _record_login_failure(request, form_data.username)
         raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid Seerr credentials")
-    jellyseerr_user_id = _extract_jellyseerr_user_id(response)
-    jellyseerr_email = _extract_jellyseerr_response_email(response)
+    jellyseerr_user_id = _extract_jellyseerr_user_id(auth_response)
+    jellyseerr_email = _extract_jellyseerr_response_email(auth_response)
     ci_matches = get_users_by_username_ci(form_data.username)
     preferred_match = _pick_preferred_ci_user_match(ci_matches, form_data.username)
     canonical_username = str(preferred_match.get("username") or form_data.username) if preferred_match else form_data.username
@@ -791,11 +821,11 @@ async def jellyseerr_login(request: Request, form_data: OAuth2PasswordRequestFor
         jellyseerr_user_id,
         _auth_client_ip(request),
     )
-    return {
-        "access_token": token,
-        "token_type": "bearer",
-        "user": {"username": canonical_username, "role": "user"},
-    }
+    return _auth_success_response(
+        response,
+        token,
+        {"username": canonical_username, "role": "user"},
+    )
 
 
 @router.get("/me")
@@ -803,6 +833,12 @@ async def me(current_user: dict = Depends(get_current_user)) -> dict:
     return current_user
 
 
+@router.post("/logout")
+async def logout(response: Response) -> dict:
+    clear_auth_cookies(response)
+    return {"status": "ok"}
+
+
 @router.get("/stream-token")
 async def stream_token(current_user: dict = Depends(get_current_user)) -> dict:
     token = create_stream_token(
@@ -832,7 +868,7 @@ async def invite_details(code: str) -> dict:
 
 
 @router.post("/signup")
-async def signup(payload: dict) -> dict:
+async def signup(payload: dict, response: Response) -> dict:
     if not isinstance(payload, dict):
         raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Invalid payload")
     invite_code = str(payload.get("invite_code") or "").strip()
@@ -908,14 +944,14 @@ async def signup(payload: dict) -> dict:
             duplicate_like = status_code in {400, 409}
             if duplicate_like:
                 try:
-                    response = await jellyfin_client.authenticate_by_name(username, password_value)
+                    auth_response = await jellyfin_client.authenticate_by_name(username, password_value)
                 except Exception as auth_exc:
                     detail = _extract_http_error_detail(auth_exc) or _extract_http_error_detail(exc)
                     raise HTTPException(
                         status_code=status.HTTP_409_CONFLICT,
                         detail=f"Jellyfin account already exists and could not be authenticated: {detail}",
                     ) from exc
-                if not isinstance(response, dict) or not response.get("User"):
+                if not isinstance(auth_response, dict) or not auth_response.get("User"):
                     raise HTTPException(
                         status_code=status.HTTP_409_CONFLICT,
                         detail="Jellyfin account already exists for that username.",
@@ -987,17 +1023,17 @@ async def signup(payload: dict) -> dict:
         created_user.get("profile_id") if created_user else None,
         invite.get("code"),
     )
-    return {
-        "access_token": token,
-        "token_type": "bearer",
-        "user": {
+    return _auth_success_response(
+        response,
+        token,
+        {
             "username": username,
             "role": role,
             "auth_provider": created_user.get("auth_provider") if created_user else auth_provider,
             "profile_id": created_user.get("profile_id") if created_user else None,
             "expires_at": created_user.get("expires_at") if created_user else None,
         },
-    }
+    )
 
 
 @router.post("/password/forgot")
diff --git a/backend/app/routers/feedback.py b/backend/app/routers/feedback.py
index d523e43..b42f066 100644
--- a/backend/app/routers/feedback.py
+++ b/backend/app/routers/feedback.py
@@ -3,6 +3,7 @@ import httpx
 from fastapi import APIRouter, Depends, HTTPException
 
 from ..auth import get_current_user
+from ..network_security import validate_notification_target_url
 from ..runtime import get_runtime_settings
 
 router = APIRouter(prefix="/feedback", tags=["feedback"], dependencies=[Depends(get_current_user)])
@@ -17,6 +18,10 @@ async def send_feedback(payload: Dict[str, Any], user: Dict[str, str] = Depends(
     )
     if not webhook_url:
         raise HTTPException(status_code=400, detail="Discord webhook not configured")
+    try:
+        webhook_url = validate_notification_target_url(webhook_url)
+    except ValueError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
 
     feedback_type = str(payload.get("type") or "").strip().lower()
     if feedback_type not in {"bug", "feature"}:
diff --git a/backend/app/services/diagnostics.py b/backend/app/services/diagnostics.py
index 9184045..394c527 100644
--- a/backend/app/services/diagnostics.py
+++ b/backend/app/services/diagnostics.py
@@ -17,6 +17,7 @@ from ..clients.radarr import RadarrClient
 from ..clients.sonarr import SonarrClient
 from ..config import settings as env_settings
 from ..db import get_database_diagnostics
+from ..network_security import validate_notification_target_url
 from ..runtime import get_runtime_settings
 from .invite_email import send_test_email, smtp_email_config_ready, smtp_email_delivery_warning
 
@@ -97,7 +98,12 @@ def _config_status(detail: str) -> str:
 def _discord_config_ready(runtime) -> tuple[bool, str]:
     if not runtime.magent_notify_enabled or not runtime.magent_notify_discord_enabled:
         return False, "Discord notifications are disabled."
-    if _clean_text(runtime.magent_notify_discord_webhook_url) or _clean_text(runtime.discord_webhook_url):
+    webhook_url = _clean_text(runtime.magent_notify_discord_webhook_url) or _clean_text(runtime.discord_webhook_url)
+    if webhook_url:
+        try:
+            validate_notification_target_url(webhook_url)
+        except ValueError as exc:
+            return False, str(exc)
         return True, "ok"
     return False, "Discord webhook URL is required."
 
@@ -113,7 +119,12 @@ def _telegram_config_ready(runtime) -> tuple[bool, str]:
 def _webhook_config_ready(runtime) -> tuple[bool, str]:
     if not runtime.magent_notify_enabled or not runtime.magent_notify_webhook_enabled:
         return False, "Generic webhook notifications are disabled."
-    if _clean_text(runtime.magent_notify_webhook_url):
+    webhook_url = _clean_text(runtime.magent_notify_webhook_url)
+    if webhook_url:
+        try:
+            validate_notification_target_url(webhook_url)
+        except ValueError as exc:
+            return False, str(exc)
         return True, "ok"
     return False, "Generic webhook URL is required."
 
@@ -123,11 +134,21 @@ def _push_config_ready(runtime) -> tuple[bool, str]:
         return False, "Push notifications are disabled."
     provider = _clean_text(runtime.magent_notify_push_provider, "ntfy").lower()
     if provider == "ntfy":
-        if _clean_text(runtime.magent_notify_push_base_url) and _clean_text(runtime.magent_notify_push_topic):
+        push_url = _clean_text(runtime.magent_notify_push_base_url)
+        if push_url and _clean_text(runtime.magent_notify_push_topic):
+            try:
+                validate_notification_target_url(push_url)
+            except ValueError as exc:
+                return False, str(exc)
             return True, "ok"
         return False, "ntfy requires a base URL and topic."
     if provider == "gotify":
-        if _clean_text(runtime.magent_notify_push_base_url) and _clean_text(runtime.magent_notify_push_token):
+        push_url = _clean_text(runtime.magent_notify_push_base_url)
+        if push_url and _clean_text(runtime.magent_notify_push_token):
+            try:
+                validate_notification_target_url(push_url)
+            except ValueError as exc:
+                return False, str(exc)
             return True, "ok"
         return False, "Gotify requires a base URL and app token."
     if provider == "pushover":
@@ -135,7 +156,12 @@ def _push_config_ready(runtime) -> tuple[bool, str]:
             return True, "ok"
         return False, "Pushover requires an application token and user key."
     if provider == "webhook":
-        if _clean_text(runtime.magent_notify_push_base_url):
+        push_url = _clean_text(runtime.magent_notify_push_base_url)
+        if push_url:
+            try:
+                validate_notification_target_url(push_url)
+            except ValueError as exc:
+                return False, str(exc)
             return True, "ok"
         return False, "Webhook relay requires a target URL."
     if provider == "telegram":
@@ -190,6 +216,7 @@ async def _run_http_post(
     params: Optional[Dict[str, Any]] = None,
     headers: Optional[Dict[str, str]] = None,
 ) -> Dict[str, Any]:
+    validate_notification_target_url(url)
     async with httpx.AsyncClient(timeout=15.0, follow_redirects=True) as client:
         response = await client.post(url, json=json_payload, data=data_payload, params=params, headers=headers)
         response.raise_for_status()
diff --git a/backend/app/services/notifications.py b/backend/app/services/notifications.py
index 2b47319..5816031 100644
--- a/backend/app/services/notifications.py
+++ b/backend/app/services/notifications.py
@@ -8,6 +8,7 @@ import httpx
 
 from ..config import settings as env_settings
 from ..db import get_setting
+from ..network_security import validate_notification_target_url
 from ..runtime import get_runtime_settings
 from .invite_email import send_generic_email
 
@@ -49,6 +50,7 @@ def _portal_item_url(item_id: int) -> str:
 
 
 async def _http_post_json(url: str, payload: Dict[str, Any]) -> Dict[str, Any]:
+    validate_notification_target_url(url)
     async with httpx.AsyncClient(timeout=12.0) as client:
         response = await client.post(url, json=payload)
         response.raise_for_status()
@@ -115,6 +117,7 @@ async def _send_push(title: str, message: str, payload: Dict[str, Any]) -> Dict[
     if provider == "ntfy":
         if not base_url or not topic:
             return {"status": "skipped", "detail": "ntfy needs base URL and topic."}
+        validate_notification_target_url(base_url)
         url = f"{base_url.rstrip('/')}/{quote(topic)}"
         headers = {"Title": title, "Tags": "magent,portal"}
         async with httpx.AsyncClient(timeout=12.0) as client:
@@ -124,6 +127,7 @@ async def _send_push(title: str, message: str, payload: Dict[str, Any]) -> Dict[
     if provider == "gotify":
         if not base_url or not token:
             return {"status": "skipped", "detail": "Gotify needs base URL and token."}
+        validate_notification_target_url(base_url)
         url = f"{base_url.rstrip('/')}/message?token={quote(token)}"
         body = {"title": title, "message": message, "priority": 5, "extras": {"client::display": {"contentType": "text/plain"}}}
         result = await _http_post_json(url, body)
diff --git a/backend/tests/test_backend_quality.py b/backend/tests/test_backend_quality.py
index a5e36e2..4bcd3ef 100644
--- a/backend/tests/test_backend_quality.py
+++ b/backend/tests/test_backend_quality.py
@@ -8,6 +8,7 @@ from starlette.requests import Request
 
 from backend.app import db
 from backend.app.config import settings
+from backend.app.network_security import request_trusts_forwarded_headers, validate_notification_target_url
 from backend.app.routers import auth as auth_router
 from backend.app.routers import portal as portal_router
 from backend.app.security import PASSWORD_POLICY_MESSAGE, validate_password_policy
@@ -72,6 +73,27 @@ class PasswordPolicyTests(unittest.TestCase):
         self.assertEqual(validate_password_policy("  password123  "), "password123")
 
 
+class NetworkSecurityTests(unittest.TestCase):
+    def test_notification_targets_reject_loopback(self) -> None:
+        with self.assertRaisesRegex(ValueError, "Private or local notification targets are not allowed."):
+            validate_notification_target_url("http://127.0.0.1:8080/webhook")
+
+    def test_forwarded_headers_require_trusted_proxy(self) -> None:
+        original_enabled = settings.magent_proxy_enabled
+        original_trust = settings.magent_proxy_trust_forwarded_headers
+        original_proxies = settings.magent_proxy_trusted_proxies
+        settings.magent_proxy_enabled = True
+        settings.magent_proxy_trust_forwarded_headers = True
+        settings.magent_proxy_trusted_proxies = "127.0.0.1,::1"
+        try:
+            self.assertTrue(request_trusts_forwarded_headers("127.0.0.1"))
+            self.assertFalse(request_trusts_forwarded_headers("203.0.113.10"))
+        finally:
+            settings.magent_proxy_enabled = original_enabled
+            settings.magent_proxy_trust_forwarded_headers = original_trust
+            settings.magent_proxy_trusted_proxies = original_proxies
+
+
 class DatabaseEmailTests(TempDatabaseMixin, unittest.TestCase):
     def test_set_user_email_is_case_insensitive(self) -> None:
         created = db.create_user_if_missing(
diff --git a/frontend/app/lib/auth.ts b/frontend/app/lib/auth.ts
index 99612bf..c89bfbb 100644
--- a/frontend/app/lib/auth.ts
+++ b/frontend/app/lib/auth.ts
@@ -1,27 +1,53 @@
+const AUTH_STATE_COOKIE = 'magent_logged_in'
+
 export const getApiBase = () => process.env.NEXT_PUBLIC_API_BASE ?? '/api'
 
-export const getToken = () => {
-  if (typeof window === 'undefined') return null
-  return window.localStorage.getItem('magent_token')
+const setCookie = (name: string, value: string, maxAgeSeconds: number) => {
+  if (typeof document === 'undefined') return
+  document.cookie = `${name}=${value}; Max-Age=${maxAgeSeconds}; Path=/; SameSite=Lax`
 }
 
-export const setToken = (token: string) => {
-  if (typeof window === 'undefined') return
-  window.localStorage.setItem('magent_token', token)
+const clearCookie = (name: string) => {
+  if (typeof document === 'undefined') return
+  document.cookie = `${name}=; Max-Age=0; Path=/; SameSite=Lax`
+}
+
+export const getToken = () => {
+  if (typeof document === 'undefined') return null
+  const cookies = document.cookie.split(';').map((entry) => entry.trim())
+  const marker = cookies.find((entry) => entry.startsWith(`${AUTH_STATE_COOKIE}=`))
+  if (!marker) return null
+  const [, value] = marker.split('=', 2)
+  return value || null
+}
+
+export const setToken = (_token: string) => {
+  setCookie(AUTH_STATE_COOKIE, '1', 60 * 60 * 12)
 }
 
 export const clearToken = () => {
+  clearCookie(AUTH_STATE_COOKIE)
   if (typeof window === 'undefined') return
-  window.localStorage.removeItem('magent_token')
+  const baseUrl = getApiBase()
+  void fetch(`${baseUrl}/auth/logout`, {
+    method: 'POST',
+    credentials: 'include',
+    keepalive: true,
+  }).catch(() => undefined)
+}
+
+export const logout = async () => {
+  const baseUrl = getApiBase()
+  clearCookie(AUTH_STATE_COOKIE)
+  await fetch(`${baseUrl}/auth/logout`, {
+    method: 'POST',
+    credentials: 'include',
+  })
 }
 
 export const authFetch = (input: RequestInfo | URL, init?: RequestInit) => {
-  const token = getToken()
   const headers = new Headers(init?.headers || {})
-  if (token) {
-    headers.set('Authorization', `Bearer ${token}`)
-  }
-  return fetch(input, { ...init, headers })
+  return fetch(input, { ...init, headers, credentials: 'include' })
 }
 
 export const getEventStreamToken = async () => {
diff --git a/frontend/app/login/page.tsx b/frontend/app/login/page.tsx
index 95acf27..7cae285 100644
--- a/frontend/app/login/page.tsx
+++ b/frontend/app/login/page.tsx
@@ -42,13 +42,14 @@ export default function LoginPage() {
         method: 'POST',
         headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
         body,
+        credentials: 'include',
       })
       if (!response.ok) {
         throw new Error('Login failed')
       }
       const data = await response.json()
-      if (data?.access_token) {
-        setToken(data.access_token)
+      if (data?.authenticated) {
+        setToken('cookie')
         if (typeof window !== 'undefined') {
           window.location.href = '/'
           return
diff --git a/frontend/app/signup/page.tsx b/frontend/app/signup/page.tsx
index fdc9c8e..8ced8f6 100644
--- a/frontend/app/signup/page.tsx
+++ b/frontend/app/signup/page.tsx
@@ -106,6 +106,7 @@ function SignupPageContent() {
       const response = await fetch(`${baseUrl}/auth/signup`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
+        credentials: 'include',
         body: JSON.stringify({
           invite_code: inviteCode,
           username: username.trim(),
@@ -117,12 +118,12 @@ function SignupPageContent() {
         throw new Error(text || 'Sign-up failed')
       }
       const data = await response.json()
-      if (data?.access_token) {
-        setToken(data.access_token)
+      if (data?.authenticated) {
+        setToken('cookie')
         window.location.href = '/'
         return
       }
-      throw new Error('Sign-up did not return a token')
+      throw new Error('Sign-up did not complete')
     } catch (err) {
       console.error(err)
       setError(err instanceof Error ? err.message : 'Unable to create account.')
diff --git a/frontend/app/ui/HeaderIdentity.tsx b/frontend/app/ui/HeaderIdentity.tsx
index 5901a88..0ba8025 100644
--- a/frontend/app/ui/HeaderIdentity.tsx
+++ b/frontend/app/ui/HeaderIdentity.tsx
@@ -1,7 +1,7 @@
 'use client'
 
 import { useEffect, useState } from 'react'
-import { authFetch, clearToken, getApiBase, getToken } from '../lib/auth'
+import { authFetch, clearToken, getApiBase, getToken, logout } from '../lib/auth'
 
 export default function HeaderIdentity() {
   const [identity, setIdentity] = useState<{ username: string; role?: string } | null>(null)
@@ -49,7 +49,8 @@ export default function HeaderIdentity() {
 
   const label = `${identity.username}${identity.role ? ` (${identity.role})` : ''}`
   const initial = identity.username.slice(0, 1).toUpperCase()
-  const signOut = () => {
+  const signOut = async () => {
+    await logout().catch(() => undefined)
     clearToken()
     if (typeof window !== 'undefined') {
       window.location.href = '/login'
@@ -83,7 +84,7 @@ export default function HeaderIdentity() {
             <a href="/changelog" onClick={() => setOpen(false)}>
               Changelog
             </a>
-            <button type="button" className="signed-in-signout" onClick={signOut}>
+            <button type="button" className="signed-in-signout" onClick={() => void signOut()}>
               Sign out
             </button>
           </div>