A01: Broken Access Control in Next.js
Next.js API routes and server actions are particularly susceptible to broken access control if developers assume that client-side routing provides security. Server-side checks must be implemented on every API route, server action, and middleware. Use Next.js middleware for route protection, but always verify permissions at the data access layer. Never rely on client-side checks alone.
Common pitfalls: Exposing admin API routes without authentication checks, trusting user IDs from request parameters without verification, and forgetting to protect Server Actions with session validation.
A03: Injection Flaws in Server Components
While React Server Components (RSC) reduce client-side attack surface, they don't eliminate injection risks. Server Components that directly query databases, read files, or execute shell commands are vulnerable to SQL injection, NoSQL injection, and command injection if input is not properly sanitised.
Mitigation: Use parameterised queries for all database operations, validate and sanitise all user inputs on the server, and avoid constructing shell commands from user-supplied data. Next.js's built-in CSRF protection for Server Actions should always be enabled.
A05: Security Misconfiguration
Common Next.js misconfigurations include exposing environment variables to the client (NEXT_PUBLIC_* misuse), leaving debug endpoints enabled in production, misconfigured CORS policies, and missing security headers. The Next.js security headers guide recommends strict CSP, HSTS, X-Frame-Options, and X-Content-Type-Options.
Tools: Use `next lint` with security plugins, implement Content Security Policy headers via next.config.mjs, and audit your bundle for exposed secrets.
Security-First Next.js Development with Cyronix
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