Securing Next.js 15 App Router Endpoints

Overview of Next.js 15 Security

Next.js 15 brings powerful compilation updates, but dynamic server routing introduces fresh vulnerability considerations. When dealing with mutation APIs, security layers should never be left to chance.

1. Implementing Content Security Policies (CSP)

By configuring strict headers, you prevent malicious XSS payloads from executing. ``typescript // src/middleware.ts import { NextResponse } from 'next/server'; export function middleware(request: Request) { const nonce = Buffer.from(crypto.randomUUID()).toString('base64'); const cspHeader = default-src 'self'; script-src 'self' 'nonce-${nonce}'; style-src 'self' 'unsafe-inline'; object-src 'none'; ; const response = NextResponse.next(); response.headers.set('Content-Security-Policy', cspHeader.replace(/\s{2,}/g, ' ')); return response; } ``

2. Form Input Sanitization

Always sanitize raw string structures client-side and server-side. Prevent SQL injections by utilizing prepared database statements and Row Level Security templates in Supabase.