Securing Next.js Applications: The Complete Guide

Why Next.js Security Matters

Next.js powers millions of applications. Its hybrid rendering and API routes create a unique attack surface.

Security Headers

Add these to your next.config.js:

• Content-Security-Policy — prevents XSS
• Strict-Transport-Security — forces HTTPS
• X-Content-Type-Options: nosniff
• X-Frame-Options: DENY
• Referrer-Policy: strict-origin-when-cross-origin

API Route Security

Authentication

Every API route needs auth checking. Next.js doesn't add this automatically.

Input Validation

Use Zod to validate every request body. Never trust client data.

Rate Limiting

Protect login, signup, and password reset endpoints.

Server Actions Security

Server Actions execute on the server but are triggered from the client. Validate all inputs and check authentication.

Environment Variables

NEXT_PUBLIC_ variables are exposed to the client — never put secrets here.

Common Mistakes

1. Using dangerouslySetInnerHTML without sanitisation
2. Exposing database queries in client components
3. Missing auth on dynamic routes
4. Logging sensitive data

VibeTrace scans Next.js projects specifically, understanding the framework's unique patterns and common pitfalls.