Individual skill
offensive-jwt
JWT attack methodology for penetration testers. Covers algorithm confusion (alg:none, RS256→HS256), weak HMAC secret brute force, kid parameter injection (SQLi, path traversal), jku/x5u/jwk header injection, JWKS cache poisoning, JWS/JWE confusion, timing attacks, and mobile JWT storage extraction. Use when testing JWT-based authentication, hunting auth bypass via token manipulation, or evaluating JWT implementation security in web or mobile apps.
Skills/auth/offensive-jwt/SKILL.md
Source commit a8de813edc9f66f60d44cfe42d47750e89d9930b
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- Yes
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- No
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- Observed behavior
- Not checked yet
- Last checked
- Nov 2, 2026
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Repository context
- Repository stars (not skill ratings)
- 10,497
- Repository last updated
- Oct 12, 2026
- License
- MIT
Observed agent integration: No specific integration evidence. Standard SKILL.md installation does not imply verified compatibility.
- claude-ai Repository topic
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- security Derived category
- testing Derived category
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Read excerpt
## Overview
Comprehensive JWT attack checklist for offensive security engagements. Follow steps in order; apply each technique to the current target context and track which items have been completed.
## Quick Reference: Misconfigurations to Check
- Algorithm set to `none` — signature verification bypassed entirely
- Algorithm switching between `RSA` and `HMAC` (confusion attack)
- Weak or guessable HMAC secret (brute-forceable)
- `kid`, `jku`, `jwk`, `x5u` header parameters accepted without validation
- Expired or tampered tokens accepted by server
- Sensitive data stored unencrypted in payload
Useful tool: [JWT Tool](https://github.com/ticarpi/jwt_tool)