API Security Hardening Checklist
Identity & access Enforce strong auth (OIDC/JWT); short-lived tokens + refresh; audience/issuer checks. Fine-grained authz (RBAC/ABAC); deny-by-default; rate-limit per identity. Input & data Validate/normalize input; reject oversized bodies; JSON schema where possible. Output encode; avoid reflecting raw user data; paginate results. Store secrets in vault/KMS; rotate keys; never log secrets/tokens. Transport & headers TLS everywhere; HSTS; modern ciphers. Security headers: Content-Security-Policy, X-Content-Type-Options=nosniff, X-Frame-Options=DENY, Referrer-Policy. Abuse protection Rate limit + burst control; CAPTCHA/step-up for sensitive actions. Bot detection where relevant; geo/IP allow/deny for admin surfaces. Observability Structured audit logs with identity, action, resource, result; avoid PII spill. Alerts on auth failures, unusual rate spikes, and 5xx anomalies. Checklist AuthZ enforced; least privilege. Input validated; size limits set. TLS + security headers applied. Rate limits + abuse controls configured. Secrets vaulted and rotated.