bounty-api

bounty-api is a skill for Claude Code from 26zl/cybersec-toolkit. It costs 77 tokens per session (1,303 once invoked), scanned A, original, MIT.

A testing guide for REST, GraphQL, gRPC, and WebSocket APIs. APIs are interfaces that let software exchange data and request actions.

In plain words
What is it for?
It is for authorized API bug-bounty testing, including endpoint discovery, schema inspection, token checks, and testing whether users can access or change other users’ data.
Why use it?
It provides a repeatable way to find authorization, authentication, rate-limit, and input-handling problems in APIs.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Part of the cybersec-toolkit plugin — 197 skills, 2 hooks, 1 MCP server shipped together

Good fit It is for authorized API bug-bounty testing, including endpoint discovery, schema inspection, token checks, and testing whether users can access or change other users’ data.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/26zl/cybersec-toolkit/bounty-api
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add 26zl/cybersec-toolkit --skill bounty-api
Clone the repo
git clone --depth 1 https://github.com/26zl/cybersec-toolkit

Made for: Claude Code.

Or install cybersec-toolkit, the plugin that ships this one along with the rest of its 197 skills, 2 hooks, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for bounty-api

README.md
[![agentmods](https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/bounty-api/github.svg)](https://agentmods.dev/skills/26zl/cybersec-toolkit/bounty-api)
Your own site
<a href="https://agentmods.dev/skills/26zl/cybersec-toolkit/bounty-api"><img src="https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/bounty-api/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for bounty-api

Your own site · 80×15
<a href="https://agentmods.dev/skills/26zl/cybersec-toolkit/bounty-api"><img src="https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/bounty-api.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 77 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,303 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 3 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Tool Misuse · line 66
    Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).
    Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
  • high YARA Match · line 132
    YARA rule matched a hack tool or exploit indicator (offensive tools, reconnaissance, privilege escalation, or exploit frameworks).
    Fix: Remove offensive tool references and exploit code. Legitimate agent skills should not contain penetration testing tools, exploit frameworks, or reconnaissance utilities.
  • medium Data Exfiltration · line 22
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00077 $0.01303
Opus 5 $0.00039 $0.00651
Sonnet 5 $0.00015 $0.00261
Haiku 4.5 $0.00008 $0.00130

Measured 5d ago against content hash cf306652da76, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

bounty-api scanned grade A with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Sends data to an external URLlowData exfiltration

A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.

curl -X POST https://target.com/graphql -d '{"query":"{__schema{types{name}}}"}'

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl https://target.com/swagger.json
.claude/skills/bounty-api/SKILL.md · 137 lines

How it starts

The opening of the file, as written. The whole thing — 137 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Bug bounty API testing

1. Discover the API

# Mobile app reverse → APK / IPA → look for endpoints
# JS bundle inspection
katana -u https://target.com -jc -silent | grep -E "/api/|/v1/|/graphql"
LinkFinder -i https://target.com/app.js -o cli

# Common paths
ffuf -w api-paths.txt -u https://target.com/FUZZ -mc 200,401,403
# /api, /api/v1, /v1, /graphql, /rest, /rpc, /swagger.json, /openapi.json,
# /api-docs, /redoc, /docs, /.well-known/

# Schema endpoints (huge if found)
curl https://target.com/swagger.json
curl https://target.com/openapi.json
curl -X POST https://target.com/graphql -d '{"query":"{__schema{types{name}}}"}'

If you find a swagger/openapi/graphql introspection — that IS the attack surface map. Use kiterunner to brute API routes if not.

2. OWASP API Top 10 — checklist per endpoint

API1: Broken Object Level Authorization (BOLA)

For every endpoint with an ID:

# Login as user A. Get user B's resource.
curl -H "Authorization: Bearer $A_TOKEN" https://api/users/$B_ID

Try: numeric→numeric swap, UUID enumeration via Wayback/JS, encoded ID decoding.

API2: Broken Authentication

  • Missing / weak JWT verification
  • Token reuse after logout
  • Refresh-token abuse
  • Hardcoded API keys in mobile bundles

API3: Broken Object Property Level (Mass Assignment + Excessive Data Exposure)

Mass assignment:

# Sign-up sends: {"email": "...", "password": "..."}
# Try: {"email": "...", "password": "...", "is_admin": true, "role": "admin"}

Excessive exposure: GET /users/me returns entire user object including hashed password / secret_question_answer / internal_notes — report it.

API4: Unrestricted Resource Consumption

Endpoints that allow ?limit=99999, deeply nested GraphQL queries, expensive operations without rate limit.

API5: Broken Function Level Authorization (BFLA)

Admin endpoints (POST /admin/users, DELETE /admin/posts/N) accessed as regular user.

API6: Unrestricted Access to Sensitive Business Flows

Read the full file on GitHub · 137 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 137 lines · 77 tokens per session scan A cf306652da76

Subscribe to this mod's changes

bounty-api is a skill published in the GitHub repository 26zl/cybersec-toolkit (49 stars, last pushed yesterday), licensed MIT. It adds 77 tokens to every session and 1,303 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 2 findings (sends data to an external url, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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