API authentication and JWT abuse playbook. Use when testing bearer tokens, API keys, claim trust, header spoofing, rate limits, and API auth boundary weaknesses.

SKILL: API Auth and JWT Abuse — Token Trust, Header Tricks, and Rate Limits AI LOAD INSTRUCTION : Use this skill when APIs rely on JWT, bearer tokens, API keys, or weak request identity signals. Focus on token trust boundaries, claim misuse, header spoofing, and rate limit bypass. 1. TOKEN TRIAGE Inspect: alg , kid , jku , x5u role, org, tenant, scope, or privilege claims issuer and audience mismatches reuse of mobile and web tokens across products 2. QUICK ATTACK PICKS Pattern First Test alg:none acceptance unsigned token with trailing dot RS256 confusion switch to HS256 using public key as secret kid lookup trust path traversal or injection in kid remote key fetch trust attacker controlled jku or x5u weak secret offline crack with targeted wordlists 3. HIDDEN FIELDS AND BATCH ABUSE Mass assignment field picks Rate limit and batch abuse picks GraphQL or JSON batch abuse candidates: arrays of login mutations bulk object fetches with varying IDs repeated password reset or verification calls in one request 4. RATE LIMIT BYPASS FAMILIES 5. NEXT ROUTING For GraphQL batching and hidden parameters: [graphql and hidden parameters](../graphql and hidden parameters/SKILL.md) For default credential and brute force planning: [authentication bypass](../authbypass authentication flaws/SKILL.md) For full JWT and OAuth depth: [jwt oauth token attacks](../jwt oauth token attacks/SKILL.md) For OAuth or OIDC configuration flaws in browser and SSO flows: [oauth oidc misconfiguration](../oauth oidc misconfiguration/SKILL.md) For credentialed browser reads and origin trust bugs: [cors cross origin misconfiguration](../cors cross origin misconfiguration/SKILL.md)

api-auth-and-jwt-abuse