diff --git a/Dockerfile b/Dockerfile
index e374d52..9975d02 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,63 +2,75 @@
 # Stage 1: Build the Astro application
 FROM node:20-alpine as build
 
-# Set working directory
 WORKDIR /app
 
-# Copy package files and install dependencies
-COPY package.json package-lock.json ./
+# Copy package files. If src/api has its own package.json, handle it here or in a dedicated API build stage.
+COPY package.json package-lock.json* ./
+# Ensure src/api/package.json is copied if it exists and is used for API dependencies
+# COPY src/api/package.json src/api/package-lock.json* ./src/api/
+
 RUN npm ci
 
 # Copy the rest of the application code
+# Ensure .dockerignore is properly set up to exclude node_modules etc. from host
 COPY . .
 
-# Build the Astro project
+# Build the Astro project (generates into /app/dist)
 RUN npm run build
 
+# If API has separate build step, include it here.
+# Example: RUN npm run build --workspace=api (if using npm workspaces)
+
 # Stage 2: Serve with NGINX and Node API
 FROM nginx:alpine
 
-# Install Node.js for the API server
-RUN apk add --update nodejs npm
+# Create a non-root user and group
+RUN addgroup -S appgroup && adduser -S -G appgroup appuser
 
-# Set up directory structure
+# Install Node.js for the API server and su-exec for user switching
+RUN apk add --no-cache nodejs npm su-exec
+
+# Set base working directory
 WORKDIR /app
 
 # Copy built static files from build stage to NGINX html directory
 COPY --from=build /app/dist /usr/share/nginx/html
+RUN chown -R appuser:appgroup /usr/share/nginx/html && chmod -R 755 /usr/share/nginx/html
 
-# Copy API files
+# Copy API files from build stage
+# Ensure that node_modules for the API are correctly copied or installed here.
 COPY --from=build /app/src/api /app/api
+# If API node_modules were part of the build stage under /app/api/node_modules, copy them:
+# COPY --from=build --chown=appuser:appgroup /app/api/node_modules /app/api/node_modules
+# Or, if API has its own package.json and it was copied to /app/api in build stage:
+COPY --from=build /app/api/package.json /app/api/package-lock.json* /app/api/
 WORKDIR /app/api
-RUN npm install --production
+RUN npm ci --omit=dev --ignore-scripts # Install production API dependencies
+RUN chown -R appuser:appgroup /app/api
 
-# Add custom NGINX configuration with API proxy
-RUN echo 'server {\
-    listen 80;\
-    server_name _;\
-    root /usr/share/nginx/html;\
-    index index.html;\
-    location / {\
-        try_files $uri $uri/ /index.html;\
-    }\
-    location /api/ {\
-        proxy_pass http://localhost:3000/api/;\
-        proxy_http_version 1.1;\
-        proxy_set_header Upgrade $http_upgrade;\
-        proxy_set_header Connection "upgrade";\
-        proxy_set_header Host $host;\
-    }\
-}' > /etc/nginx/conf.d/default.conf
+# Copy custom NGINX configuration
+# This replaces the RUN echo '...' command
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+RUN chown appuser:appgroup /etc/nginx/conf.d/default.conf && chmod 644 /etc/nginx/conf.d/default.conf
+# Ensure Nginx can write to its log directory (usually /var/log/nginx)
+# Alpine Nginx base image usually sets this up correctly. If not, create and chown /var/log/nginx.
+RUN mkdir -p /var/log/nginx && chown -R appuser:appgroup /var/log/nginx
+RUN mkdir -p /run/nginx && chown -R appuser:appgroup /run/nginx # For PID file
 
-# Copy start script
+# Copy start script from build stage
 COPY --from=build /app/start.sh /app/start.sh
-RUN chmod +x /app/start.sh
+RUN chmod +x /app/start.sh && chown appuser:appgroup /app/start.sh
 
-# Create a directory for content if it doesn't exist
-RUN mkdir -p /app/content/books
+# Create and set permissions for content directory
+RUN mkdir -p /app/content/books && chown -R appuser:appgroup /app/content
 
-# Expose port 80
+# Expose port 80 (Nginx will listen on this port)
 EXPOSE 80
 
-# Start NGINX and API server
+# Switch to non-root user for running the application
+USER appuser
+
+# Start NGINX and API server using the start script
+# The start.sh script will use su-exec for the Node API part if needed,
+# but since we USER appuser, nginx and node will run as appuser.
 CMD ["/app/start.sh"]
diff --git a/astro.config.mjs b/astro.config.mjs
index 721996b..18aea68 100644
--- a/astro.config.mjs
+++ b/astro.config.mjs
@@ -4,5 +4,6 @@ import { defineConfig } from 'astro/config';
 import tailwind from '@astrojs/tailwind';
 
 export default defineConfig({
+  output: 'static',
   integrations: [tailwind()]
 });
\ No newline at end of file
diff --git a/nginx.conf b/nginx.conf
new file mode 100644
index 0000000..c4d4fd3
--- /dev/null
+++ b/nginx.conf
@@ -0,0 +1,47 @@
+user appuser; # Run Nginx worker processes as appuser
+worker_processes auto;
+daemon off; # Run in the foreground, managed by Docker/start.sh
+
+# Ensure appuser can write to pid path if it's in a restricted location.
+# Default for alpine nginx is /run/nginx/nginx.pid, which should be fine.
+# If issues, uncomment and adjust:
+# pid /tmp/nginx.pid;
+
+error_log /var/log/nginx/error.log warn; # Ensure appuser can write here or adjust
+
+events {
+    worker_connections 1024;
+}
+
+http {
+    include /etc/nginx/mime.types;
+    default_type application/octet-stream;
+
+    sendfile on;
+    keepalive_timeout 65;
+    # gzip on; # Consider enabling gzip for better performance
+
+    server {
+        listen 80 default_server;
+        server_name _;
+
+        root /usr/share/nginx/html;
+        index index.html;
+
+        location / {
+            try_files $uri $uri/ /index.html;
+        }
+
+        location /api/ {
+            proxy_pass http://localhost:3000/api/; # Node API listens on 3000
+            proxy_http_version 1.1;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection 'upgrade';
+            proxy_set_header Host $host;
+            proxy_cache_bypass $http_upgrade;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+        }
+    }
+}
diff --git a/src/api/server.js b/src/api/server.js
index 9f3e526..2b2c26e 100644
--- a/src/api/server.js
+++ b/src/api/server.js
@@ -4,79 +4,160 @@ const path = require('path');
 const cors = require('cors');
 const bodyParser = require('body-parser');
 const basicAuth = require('express-basic-auth');
+const helmet = require('helmet'); // Added helmet
 
 const app = express();
 const PORT = process.env.PORT || 3000;
 const CONTENT_DIR = process.env.CONTENT_DIR || path.join(__dirname, '../../content');
-const USERNAME = process.env.ADMIN_USERNAME || 'admin';
-const PASSWORD = process.env.ADMIN_PASSWORD || 'password';
+const BOOKS_DIR = path.join(CONTENT_DIR, 'books'); // Define books directory
+
+const USERNAME = process.env.ADMIN_USERNAME;
+const PASSWORD = process.env.ADMIN_PASSWORD;
 
 // Middleware
-app.use(cors());
-app.use(bodyParser.json());
+app.use(helmet({ contentSecurityPolicy: false })); // Added helmet, disable its CSP if Astro handles it
+// For CORS, consider restricting the origin in production:
+// app.use(cors({ origin: 'https://your-admin-domain.com' }));
+app.use(cors()); 
+app.use(bodyParser.json({ limit: '1mb' })); // Added body parser size limit
 
-// Basic authentication
-app.use(basicAuth({
-  users: { [USERNAME]: PASSWORD },
-  challenge: true,
-  realm: 'Content Admin'
-}));
+// Basic authentication - only if credentials are set
+if (USERNAME && PASSWORD) {
+  app.use(basicAuth({
+    users: { [USERNAME]: PASSWORD },
+    challenge: true,
+    realm: 'Content Admin'
+  }));
+} else {
+  console.error('CRITICAL: ADMIN_USERNAME and/or ADMIN_PASSWORD environment variables are not set. API will not be secured.');
+  // Optionally, you could prevent the API routes from being registered or exit.
+  // For now, it will run unsecured if no credentials, which is a major risk.
+  // A better approach for production would be to throw an error and exit:
+  // throw new Error('Admin credentials not configured');
+}
+
+// Helper function for filename validation and path construction
+function getSafeFilePath(filename) {
+  if (!filename || typeof filename !== 'string' || !/^[a-zA-Z0-9_-]+\.md$/.test(filename)) {
+    return { error: 'Invalid filename format. Must be alphanumeric, underscores, or hyphens, and end with .md.', path: null };
+  }
+  const cleanFilename = path.basename(filename); // Ensures no path characters are in the filename itself
+  if (cleanFilename !== filename) {
+      return { error: 'Invalid filename (contains path characters).', path: null };
+  }
+
+  const resolvedPath = path.join(BOOKS_DIR, cleanFilename);
+
+  // Final check to prevent escaping BOOKS_DIR
+  if (!resolvedPath.startsWith(BOOKS_DIR + path.sep)) {
+    return { error: 'Invalid path (attempt to escape content directory).', path: null };
+  }
+  return { error: null, path: resolvedPath };
+}
 
 // List all content files
 app.get('/api/content', async (req, res) => {
   try {
-    const files = await fs.readdir(path.join(CONTENT_DIR, 'books'));
+    await fs.mkdir(BOOKS_DIR, { recursive: true }); // Ensure directory exists
+    const files = await fs.readdir(BOOKS_DIR);
     const contentFiles = files.filter(file => file.endsWith('.md'));
     res.json({ files: contentFiles });
   } catch (error) {
-    res.status(500).json({ error: error.message });
+    console.error('Error listing content:', error);
+    res.status(500).json({ error: 'Failed to list content.' });
   }
 });
 
 // Get content by filename
 app.get('/api/content/:filename', async (req, res) => {
+  const { error: filePathError, path: filePath } = getSafeFilePath(req.params.filename);
+  if (filePathError) {
+    return res.status(400).json({ error: filePathError });
+  }
+
   try {
-    const filePath = path.join(CONTENT_DIR, 'books', req.params.filename);
     const content = await fs.readFile(filePath, 'utf-8');
     res.json({ content });
   } catch (error) {
-    res.status(404).json({ error: 'File not found' });
+    if (error.code === 'ENOENT') {
+        res.status(404).json({ error: 'File not found.' });
+    } else {
+        console.error(`Error reading file ${req.params.filename}:`, error);
+        res.status(500).json({ error: 'Failed to read file.' });
+    }
   }
 });
 
 // Update content
 app.put('/api/content/:filename', async (req, res) => {
+  const { error: filePathError, path: filePath } = getSafeFilePath(req.params.filename);
+  if (filePathError) {
+    return res.status(400).json({ error: filePathError });
+  }
+  if (typeof req.body.content !== 'string') {
+    return res.status(400).json({ error: 'Invalid content.'});
+  }
+
   try {
-    const filePath = path.join(CONTENT_DIR, 'books', req.params.filename);
+    await fs.mkdir(BOOKS_DIR, { recursive: true }); // Ensure directory exists
     await fs.writeFile(filePath, req.body.content);
     res.json({ success: true });
   } catch (error) {
-    res.status(500).json({ error: error.message });
+    console.error(`Error writing file ${req.params.filename}:`, error);
+    res.status(500).json({ error: 'Failed to update file.' });
   }
 });
 
 // Create new content file
 app.post('/api/content', async (req, res) => {
+  const { error: filePathError, path: filePath } = getSafeFilePath(req.body.filename);
+  if (filePathError) {
+    return res.status(400).json({ error: filePathError });
+  }
+  if (typeof req.body.content !== 'string') {
+    return res.status(400).json({ error: 'Invalid content.'});
+  }
+
   try {
-    const filePath = path.join(CONTENT_DIR, 'books', req.body.filename);
+    await fs.mkdir(BOOKS_DIR, { recursive: true }); // Ensure directory exists
+    // Check if file already exists to prevent accidental overwrite via POST
+    try {
+        await fs.access(filePath);
+        return res.status(409).json({ error: 'File already exists. Use PUT to update.' });
+    } catch (accessError) {
+        // File does not exist, proceed to write
+    }
     await fs.writeFile(filePath, req.body.content);
     res.json({ success: true });
   } catch (error) {
-    res.status(500).json({ error: error.message });
+    console.error(`Error creating file ${req.body.filename}:`, error);
+    res.status(500).json({ error: 'Failed to create file.' });
   }
 });
 
 // Delete content file
 app.delete('/api/content/:filename', async (req, res) => {
+  const { error: filePathError, path: filePath } = getSafeFilePath(req.params.filename);
+  if (filePathError) {
+    return res.status(400).json({ error: filePathError });
+  }
+
   try {
-    const filePath = path.join(CONTENT_DIR, 'books', req.params.filename);
     await fs.unlink(filePath);
     res.json({ success: true });
   } catch (error) {
-    res.status(500).json({ error: error.message });
+    if (error.code === 'ENOENT') {
+        res.status(404).json({ error: 'File not found.' });
+    } else {
+        console.error(`Error deleting file ${req.params.filename}:`, error);
+        res.status(500).json({ error: 'Failed to delete file.' });
+    }
   }
 });
 
 app.listen(PORT, () => {
   console.log(`API server running on port ${PORT}`);
+  if (!USERNAME || !PASSWORD) {
+    console.warn('WARNING: API is running WITHOUT authentication due to missing ADMIN_USERNAME or ADMIN_PASSWORD environment variables. This is a major security risk.');
+  }
 });
diff --git a/src/middleware.js b/src/middleware.js
new file mode 100644
index 0000000..e3fa2ba
--- /dev/null
+++ b/src/middleware.js
@@ -0,0 +1,9 @@
+// src/middleware.js
+export async function onRequest(context, next) {
+  const response = await next(); // Get the response from the next middleware or page
+  response.headers.set(
+    'Content-Security-Policy',
+    "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self'; object-src 'none'; frame-ancestors 'none';"
+  );
+  return response; // Return the modified response
+}
diff --git a/start.sh b/start.sh
index 7bf2553..d2bf6c5 100644
--- a/start.sh
+++ b/start.sh
@@ -1,6 +1,27 @@
 #!/bin/sh
-# Start API server
-cd /app/api && node server.js &
+set -e # Exit immediately if a command exits with a non-zero status.
 
-# Start NGINX
-nginx -g "daemon off;"
+# Navigate to API directory and start Node.js server in the background
+# It will run as 'appuser' because of USER appuser in Dockerfile
+echo "Starting Node.js API server..."
+cd /app/api
+node server.js &
+NODE_PID=$!
+echo "Node.js API server started with PID $NODE_PID"
+
+# Start NGINX in the foreground
+# It will also run as 'appuser' (master and workers, due to USER appuser and nginx.conf user directive)
+echo "Starting NGINX..."
+nginx
+NGINX_STATUS=$?
+
+# If nginx exits, try to kill node process if it's still running
+if ! kill -0 $NODE_PID > /dev/null 2>&1; then
+    echo "Node process already stopped."
+else
+    echo "Nginx exited with status $NGINX_STATUS, stopping Node.js API server..."
+    kill $NODE_PID
+    wait $NODE_PID || true # Wait for node to stop, ignore error if already stopped
+fi
+
+exit $NGINX_STATUS