Getting Started with API Security

Reported: Nov 14, 2025

This post gathers practical notes from the APISec Certified Practitioner course and my own hands-on experience with building and testing APIs. It focuses on the essentials you should check when auditing or deploying an API.

Key Principles

  • Least privilege: Ensure tokens and API keys grant only the permissions necessary for a client’s operation.
  • Authentication & Authorization: Use strong authentication (OAuth2 / mTLS for service-to-service) and enforce authorization server-side for every protected resource.
  • Validate inputs: Treat all input as untrusted. Validate, canonicalize, and apply strict schemas (JSON Schema) on the server.
  • Rate limiting & throttling: Apply limits at the edge to mitigate misuse and automated scraping.

Quick checklist

  1. Use structured errors that avoid leaking implementation details (stack traces, internal IDs).
  2. Prefer stable public IDs instead of internal database keys in responses.
  3. Secure all administrative or sensitive endpoints behind stricter auth and IP allowlists where necessary.
  4. Log judiciously: don't store raw secrets, and redact PII from logs.
  5. Adopt automated API tests for schema validation and golden-record checks as part of CI.

Tools & techniques

Some practical tools I used:

  • API schema validation: JSON Schema, OpenAPI + contract tests
  • Static analysis & fuzzing: OWASP ZAP, Burp Suite (community/professional features), and small fuzzers
  • Rate-limiting & WAF: Cloud provider edge rules or nginx/Envoy rate limiting

If you'd like a more detailed checklist or a sample Postman / OpenAPI bundle, ask and I can add it here as a downloadable resource.

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