Treat API routes as production backend code
Next.js API routes and server actions need the same controls as any backend: authentication, authorization, input validation, payload limits, rate limiting, and structured error handling. Client-side checks are useful for UX, but they are not security boundaries.
Use secure defaults at the edge
Security headers, strict transport security, safe image sources, and a clear content security policy reduce common browser-side risks. These controls should be tested during build and reviewed whenever third-party scripts change.
Reduce dependency and secret exposure
Modern JavaScript apps move fast, so dependency reviews and secret handling must be part of delivery. Keep secrets server-side, rotate credentials, audit packages, and avoid shipping private config into browser bundles.
Monitor the app after launch
Security is not complete at deployment. Production logs, error tracking, uptime checks, alerting, and vulnerability review cycles help catch issues before customers or attackers find them.