Add HSTS and other security headers (GitbookIO#2271)

Author: jpreynat

src/middleware.ts

@@ -235,6 +235,10 @@ export async function middleware(request: NextRequest) {
 
  // Add Content Security Policy header
  response.headers.set('content-security-policy', csp);
+ // Basic security headers
+ response.headers.set('strict-transport-security', 'max-age=31536000');
+ response.headers.set('referrer-policy', 'no-referrer-when-downgrade');
+ response.headers.set('x-content-type-options', 'nosniff');
 
  const isPrefetch = request.headers.has('x-middleware-prefetch');