Securing Your Next.js App

Security is non-negotiable in modern web applications. This comprehensive guide covers securing Next.js applications from common vulnerabilities.

Authentication Strategies

Implement secure auth with NextAuth.js:

// pages/api/auth/[...nextauth].js
import NextAuth from "next-auth"
import Providers from "next-auth/providers"

export default NextAuth({
  providers: [
    Providers.Credentials({
      async authorize(credentials) {
        // Custom credential validation
      }
    }),
    Providers.Google({
      clientId: process.env.GOOGLE_ID,
      clientSecret: process.env.GOOGLE_SECRET
    })
  ],
  callbacks: {
    async jwt(token, user) {
      // Add custom claims
    }
  }
})

Authorization Patterns

Implement role-based access control:

• Middleware for route protection
• Component-level permission checks
• API route validation
• Server-side props authorization

Security Hardening

Essential security headers:

// next.config.js
module.exports = {
  async headers() {
    return [
      {
        source: '/(.*)',
        headers: [
          { key: 'X-Content-Type-Options', value: 'nosniff' },
          { key: 'X-Frame-Options', value: 'SAMEORIGIN' },
          { key: 'Content-Security-Policy', 
            value: "default-src 'self'; script-src 'self' 'unsafe-eval'" }
        ]
      }
    ]
  }
}

Data Validation and Sanitization

Prevent injection attacks:

• Zod for runtime validation
• DOMPurify for HTML sanitization
• Parameterized database queries
• Rate limiting for API routes

Follow these practices to build Next.js applications that meet enterprise security standards.