# Api Auth And Jwt Abuse

> >-

- **Type:** Skill
- **Install:** `agentstack add skill-yaklang-hack-skills-api-auth-and-jwt-abuse`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [yaklang](https://agentstack.voostack.com/s/yaklang)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [yaklang](https://github.com/yaklang)
- **Source:** https://github.com/yaklang/hack-skills/tree/main/skills/api-auth-and-jwt-abuse

## Install

```sh
agentstack add skill-yaklang-hack-skills-api-auth-and-jwt-abuse
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# 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

```text
role
isAdmin
admin
verified
plan
tier
permissions
org
owner
```

### Rate limit and batch abuse picks

```text
X-Forwarded-For: 1.2.3.4
X-Real-IP: 5.6.7.8
Forwarded: for=9.9.9.9
```

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

```text
X-Forwarded-For
X-Real-IP
Forwarded
User-Agent rotation
Path case / slash variants
```

## 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)

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [yaklang](https://github.com/yaklang)
- **Source:** [yaklang/hack-skills](https://github.com/yaklang/hack-skills)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-yaklang-hack-skills-api-auth-and-jwt-abuse
- Seller: https://agentstack.voostack.com/s/yaklang
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.