Checklist of the most important security countermeasures when designing, testing, and releasing your API.

June 4, 2026 - High-profile breaches like T-Mobile (37M records exposed) and Optus (9.8M records leaked) were not caused by advanced exploits: but by simple broken authorization and exposed API logic.

December 1, 2025 - API breaches happen because automated scanners can't detect business logic flaws. When T-Mobile exposed 37 million records, and Optus leaked 9.8 million customer details, both breaches stemmed from authorisation failures that no scanner flagged. This checklist provides 10 critical penetration tests that reveal the vulnerabilities attackers actually exploit, complete with testing methods, real breach examples, and the tools you need to find these issues before attackers do.

12 hours ago - REST-style HTTP APIs: JSON is common but not required. Look for an OpenAPI document (openapi.json, swagger.json, /api-docs) and render it with Swagger UI or import it into an HTTP client.

April 23, 2024 - During testing, a pentester discovers an undocumented parameter that allows adding arbitrary data to customer orders. This could be a vulnerability if the additional data isn’t properly sanitized and validated. Many applications rely on external APIs to function. However, if these APIs are not consumed securely, it can introduce vulnerabilities into your application. This checklist point focuses on identifying weaknesses in your application’s interaction with external APIs.

October 29, 2025 - A standardized API pentesting checklist OWASP helps organizations secure APIs with a proven framework. It ensures consistency across every layer of testing.

August 11, 2025 - The most important item in any API penetration testing checklist is planning and goal setting, as they help set the direction for the testing.

October 10, 2024 - An API pentesting security checklist serves as a comprehensive guide outlining essential security measures crucial for bolstering the protection of your APIs against potential cyber threats.

September 24, 2025 - Role-based access control (RBAC) enforcement: Verify that users cannot access admin-level APIs or modify data outside their permissions. Many pentesters overlook business logic authorization flaws, where users can perform actions they shouldn’t, such as modifying another user’s order or escalating privileges via API callsHow to Secure API Calls.

August 26, 2026 - TCM Security’s Practical API Hacking course https://portswigger.net/web-security/jwt https://owasp.org/API-Security/editions/2023/en/0x11-t10/ https://cheatsheetseries.owasp.org/cheatsheets/REST_Security_Cheat_Sheet.html https://github.com/shieldfy/API-Security-Checklist https://owasp.org/www-chapter-vancouver/assets/presentations/2020-01_Attacking_and_Securing_JWT.pdf https://owasp.org/www-chapter-belgium/assets/2021/2021-02-18/JWT-Security.pdf

July 8, 2025 - Rate Limiting Bypass: Test for missing IP whitelisting or weak rate-limiting algorithms. Example: A crypto exchange allowed unlimited API calls via header spoofing (X-Forwarded-For manipulation).

July 16, 2026 - An API penetration test must be exhaustive, covering authentication, authorization, rate limiting, data validation, and business logic flaws. Without a structured checklist, security teams risk missing critical vulnerabilities that attackers ...

Checklist for API Pentesting based on the OWASP API Security Top 10 - 0x48756773/OWASP-API-Checklist

February 26, 2026 - I recently stumbled upon a GitHub repo by Shieldify that contained an API security checklist of the most important countermeasures to consider when designing, testing, and releasing an application programming interface.

A comprehensive collection of resources designed to help you enhance the security of your APIs. In this repository, you'll find a wide range of wordlists, checklists, vulnerable app setups, Logger++ filters and resources dedicated to REST APIs, ...

A "How to Test" note plus a ready-to-fire PoC command (curl/tool) has been added to every check, so the checklist isn't just a reference — it can be copy-pasted and used directly during an actual pentest. Replace placeholders like TARGET, TOKEN, ID with your engagement's actual values. Run destructive/DoS-type PoCs only within authorized scope and with rate-limiting/caution. Fuzz for hidden/undocumented APIs at multiple levels (/api/v1/, /api/v2/, /internal/, /admin-api/).

Don't use any sensitive data (credentials, Passwords, security tokens, or API keys) in the URL, but use standard Authorization header.