diff --git a/server/index.js b/server/index.js
index cd8a215..a93508b 100644
--- a/server/index.js
+++ b/server/index.js
@@ -58,7 +58,14 @@ const { startPoller, POLL_INTERVAL, POLLING_ENABLED } = require('./utils/poller'
 const app = express();
 const PORT = process.env.PORT || 3001;
 
-app.use(cookieParser());
+const cookieSecret = process.env.COOKIE_SECRET;
+if (!cookieSecret && process.env.NODE_ENV === 'production') {
+  console.error('[Security] COOKIE_SECRET is not set in production — cookies are unsigned and can be tampered with!');
+  process.exit(1);
+} else if (!cookieSecret) {
+  console.warn('[Security] COOKIE_SECRET is not set — using unsigned cookies (acceptable for development only)');
+}
+app.use(cookieParser(cookieSecret || undefined));
 app.use(express.json());
 app.use(express.static(path.join(__dirname, '../public')));
 
diff --git a/server/middleware/requireAuth.js b/server/middleware/requireAuth.js
index 002af74..2504fcb 100644
--- a/server/middleware/requireAuth.js
+++ b/server/middleware/requireAuth.js
@@ -1,13 +1,20 @@
 function requireAuth(req, res, next) {
-  const userCookie = req.cookies.emby_user;
-  if (!userCookie) {
+  const signed = !!process.env.COOKIE_SECRET;
+  const raw = signed ? req.signedCookies.emby_user : req.cookies.emby_user;
+  if (!raw || raw === false) {
     return res.status(401).json({ error: 'Not authenticated' });
   }
+  let u;
   try {
-    req.user = JSON.parse(userCookie);
+    u = JSON.parse(raw);
   } catch {
     return res.status(401).json({ error: 'Invalid session' });
   }
+  // Schema validation
+  if (typeof u.id !== 'string' || !u.id) return res.status(401).json({ error: 'Invalid session' });
+  if (typeof u.name !== 'string' || !u.name) return res.status(401).json({ error: 'Invalid session' });
+  if (typeof u.isAdmin !== 'boolean') u.isAdmin = !!u.isAdmin;
+  req.user = u;
   next();
 }
 
diff --git a/server/routes/auth.js b/server/routes/auth.js
index aec4512..70a37a9 100644
--- a/server/routes/auth.js
+++ b/server/routes/auth.js
@@ -40,17 +40,17 @@ router.post('/login', loginLimiter, async (req, res) => {
     const user = userResponse.data;
     console.log(`[Auth] Login successful for user: ${user.Name}, isAdmin: ${!!(user.Policy && user.Policy.IsAdministrator)}`);
     
-    // Set authentication cookie
-    // Note: token is intentionally excluded from the cookie — it is not needed client-side
+    // Set authentication cookie.
+    // Note: token is intentionally excluded from the cookie — it is not needed client-side.
+    // Cookie is signed when COOKIE_SECRET is set (recommended in production).
     const isAdmin = !!(user.Policy && user.Policy.IsAdministrator);
-    res.cookie('emby_user', JSON.stringify({
-      id: user.Id,
-      name: user.Name,
-      isAdmin: isAdmin
-    }), {
+    const cookiePayload = JSON.stringify({ id: user.Id, name: user.Name, isAdmin });
+    const signed = !!process.env.COOKIE_SECRET;
+    res.cookie('emby_user', cookiePayload, {
       httpOnly: true,
       secure: process.env.NODE_ENV === 'production',
       sameSite: 'strict',
+      signed,
       maxAge: 24 * 60 * 60 * 1000 // 24 hours
     });
     
@@ -71,28 +71,30 @@ router.post('/login', loginLimiter, async (req, res) => {
   }
 });
 
+function parseSessionCookie(req) {
+  const signed = !!process.env.COOKIE_SECRET;
+  const raw = signed ? req.signedCookies.emby_user : req.cookies.emby_user;
+  if (!raw || raw === false) return null; // false = tampered signed cookie
+  try {
+    const u = JSON.parse(raw);
+    // Schema validation: require id (string), name (string), isAdmin (boolean)
+    if (typeof u.id !== 'string' || !u.id) return null;
+    if (typeof u.name !== 'string' || !u.name) return null;
+    if (typeof u.isAdmin !== 'boolean') u.isAdmin = !!u.isAdmin;
+    return u;
+  } catch {
+    return null;
+  }
+}
+
 // Get current authenticated user
 router.get('/me', (req, res) => {
-  try {
-    const userCookie = req.cookies.emby_user;
-    
-    if (!userCookie) {
-      return res.json({ authenticated: false });
-    }
-    
-    const user = JSON.parse(userCookie);
-    res.json({
-      authenticated: true,
-      user: {
-        id: user.id,
-        name: user.name,
-        isAdmin: !!user.isAdmin
-      }
-    });
-  } catch (error) {
-    console.error(`[Auth] Error getting current user:`, error.message);
-    res.json({ authenticated: false });
-  }
+  const user = parseSessionCookie(req);
+  if (!user) return res.json({ authenticated: false });
+  res.json({
+    authenticated: true,
+    user: { id: user.id, name: user.name, isAdmin: user.isAdmin }
+  });
 });
 
 // Logout
@@ -100,7 +102,8 @@ router.post('/logout', (req, res) => {
   res.clearCookie('emby_user', {
     httpOnly: true,
     secure: process.env.NODE_ENV === 'production',
-    sameSite: 'strict'
+    sameSite: 'strict',
+    signed: !!process.env.COOKIE_SECRET
   });
   res.json({ success: true });
 });
diff --git a/server/routes/dashboard.js b/server/routes/dashboard.js
index 3f93c78..cebb4fa 100644
--- a/server/routes/dashboard.js
+++ b/server/routes/dashboard.js
@@ -1,5 +1,6 @@
 const express = require('express');
 const router = express.Router();
+const requireAuth = require('../middleware/requireAuth');
 
 const axios = require('axios');
 const { mapTorrentToDownload } = require('../utils/qbittorrent');
@@ -143,15 +144,9 @@ function getActiveClients() {
 }
 
 // Get user downloads for authenticated user
-router.get('/user-downloads', async (req, res) => {
+router.get('/user-downloads', requireAuth, async (req, res) => {
   try {
-    // Get authenticated user from cookie
-    const userCookie = req.cookies.emby_user;
-    if (!userCookie) {
-      return res.status(401).json({ error: 'Not authenticated' });
-    }
-    
-    const user = JSON.parse(userCookie);
+    const user = req.user;
     const username = user.name.toLowerCase();
     const usernameSanitized = sanitizeTagLabel(user.name);
     const isAdmin = !!user.isAdmin;
@@ -622,7 +617,7 @@ router.get('/user-downloads', async (req, res) => {
 });
 
 // Get all users with their download counts
-router.get('/user-summary', async (req, res) => {
+router.get('/user-summary', requireAuth, async (req, res) => {
   try {
     const sonarrInstances = getSonarrInstances();
     const radarrInstances = getRadarrInstances();
@@ -696,13 +691,9 @@ router.get('/user-summary', async (req, res) => {
 });
 
 // Admin-only status page with cache stats
-router.get('/status', (req, res) => {
+router.get('/status', requireAuth, (req, res) => {
   try {
-    const userCookie = req.cookies.emby_user;
-    if (!userCookie) {
-      return res.status(401).json({ error: 'Not authenticated' });
-    }
-    const user = JSON.parse(userCookie);
+    const user = req.user;
     if (!user.isAdmin) {
       return res.status(403).json({ error: 'Admin access required' });
     }