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.
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tessl review fix ./Skills/auth/offensive-jwt/SKILL.mdSecurity
3 findings: 2 critical severity, 1 high severity. Installing this skill is not recommended: please review these findings carefully if you do intend to do so.
E005: Suspicious download URL detected in skill instructions.
What this means
Detected a suspicious URL in the skill instructions that could lead the agent to download and execute malicious scripts or binaries. This includes links to executables from untrusted sources, typosquatting of official packages, URL shorteners that obscure the destination, and personal file hosting services.
Why it was flagged
Two URLs point to attacker-controlled JWKS/cert endpoints (https://attacker.com/jwks.json and https://attacker.com/cert.pem) which are high-risk for JKU/x5u header injection, remote key loading, SSRF or delivering malicious payloads, so they are suspicious.
E006: Malicious code pattern detected in skill scripts.
What this means
Detected high-risk code patterns in the skill content — including its prompts, tool definitions, and resources — such as data exfiltration, backdoors, remote code execution, credential theft, system compromise, supply chain attacks, and obfuscation techniques.
Why it was flagged
This SKILL.md is an explicit offensive JWT exploitation checklist with step-by-step instructions (attacker-controlled JWKS, re-signing tokens, SQL/path injection via kid, brute-force and timing attacks, extraction commands) that enable deliberate unauthorized access, credential theft, and data exfiltration.
W007: Insecure credential handling detected in skill instructions.
What this means
The skill handles credentials insecurely by requiring the agent to include secret values verbatim in its generated output. This exposes credentials in the agent’s context and conversation history, creating a risk of data exfiltration.
Why it was flagged
The checklist repeatedly shows and instructs embedding real JWTs/API keys/tokens verbatim into headers, curl commands, and CLI args (e.g., Authorization: Bearer <token>, curl with <api_key>, jwt_tool <token>), which would require an LLM to handle and output secret values directly if it populated or relayed those values.
- Repository
- SnailSploit/Claude-Red
- Commit
24d7968
- Audited
- Security analysis
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