pentest-api-deep

pentest-api-deep is a skill for Claude Code, Codex from jd-opensource/JoySafeter. It costs 43 tokens per session (799 once invoked), scanned A, original, Apache-2.0.

A security-testing guide for application programming interfaces (APIs), the interfaces software uses to exchange data and perform actions.

In plain words
What is it for?
It is for testing REST, GraphQL, gRPC, and WebSocket APIs for permission errors, mass assignment, unsafe input handling, rate-limit problems, and risky third-party data use.
Why use it?
It helps find API-specific weaknesses beyond checking whether users can access the wrong records, including unauthorized functions, excessive data exposure, and weak rate limits.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/jd-opensource/joysafeter/pentest-api-deep
Any agent
npx skills add jd-opensource/JoySafeter --skill pentest-api-deep
Clone the repo
git clone --depth 1 https://github.com/jd-opensource/JoySafeter

Made for: Claude Code, Codex.

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 pentest-api-deep

README.md
[![agentmods](https://agentmods.dev/badge/skills/jd-opensource/joysafeter/pentest-api-deep.svg)](https://agentmods.dev/skills/jd-opensource/joysafeter/pentest-api-deep)
Your own site
<a href="https://agentmods.dev/skills/jd-opensource/joysafeter/pentest-api-deep"><img src="https://agentmods.dev/badge/skills/jd-opensource/joysafeter/pentest-api-deep.svg" alt="Measured on agentmods" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 799 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00043 $0.00799
Opus 5 $0.00022 $0.00400
Sonnet 5 $0.00009 $0.00160
Haiku 4.5 $0.00004 $0.00080

Measured 4d ago against content hash 549f60145f5f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

pentest-api-deep scanned grade A with 0 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 4d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/pentest-api-deep/SKILL.md · 63 lines

How it starts

The opening of the file, as written. The whole thing — 63 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Pentest API Deep

Purpose

Perform dedicated API-specific vulnerability testing beyond basic BOLA/GraphQL coverage. Addresses Broken Function Level Authorization (BFLA), mass assignment, rate limiting, excessive data exposure, and unsafe consumption per OWASP API Security Top 10 (2023).

Prerequisites

Authorization Requirements

  • Written authorization with API testing scope explicitly included
  • API documentation (OpenAPI/Swagger specs, GraphQL schema) if available
  • Test accounts at multiple privilege levels (user, admin, service account)
  • Rate limit awareness — confirm acceptable request volume with target owner

Environment Setup

  • Postman or Insomnia for manual API exploration
  • Burp Suite with API-specific extensions
  • GraphQL Voyager for schema visualization
  • grpcurl for gRPC service testing

Core Workflow

  1. API Discovery: Enumerate endpoints via OpenAPI/Swagger specs, GraphQL introspection, gRPC reflection, traffic analysis. Discover undocumented endpoints with Kiterunner.
  2. BFLA Testing: Access admin-only API functions as regular user. HTTP method switching (GET→DELETE). Test function-level authorization gaps distinct from object-level (BOLA).
  3. Mass Assignment: Send extra fields in POST/PUT (role, isAdmin, balance). Check response objects for leaked internal fields (WSTG-INPV-20).
  4. Rate Limiting & Resource: Test missing rate limits, GraphQL depth/complexity abuse, pagination abuse, regex DoS via API input.
  5. Excessive Data Exposure: Compare API responses across privilege levels. Identify fields returned but not displayed in UI. Test verbose error responses.
  6. Unsafe Consumption: SSRF through upstream API calls, injection through trusted-but-tainted API response data.
  7. API Versioning: Old API versions with weaker controls, version header manipulation, deprecated endpoint access.

OWASP API Security Top 10 (2023) Coverage

Category Test Focus Status
API1 Broken Object Level Authorization IDOR via API params
API2 Broken Authentication Token/key weaknesses
API3 Broken Object Property Level Authorization Mass assignment, excessive data
API4 Unrestricted Resource Consumption Rate limits, complexity
API5 Broken Function Level Authorization BFLA, method switching
API6 Unrestricted Access to Sensitive Business Flows Automation abuse
API7 Server Side Request Forgery API-triggered SSRF
API8 Security Misconfiguration CORS, headers, versioning
API9 Improper Inventory Management Shadow APIs, deprecated versions
API10 Unsafe Consumption of Third-Party APIs Upstream injection

Read the full file on GitHub · 63 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 4d ago First seen · 63 lines · 43 tokens per session scan A 549f60145f5f

Subscribe to this mod's changes

pentest-api-deep is a skill published in the GitHub repository jd-opensource/JoySafeter (305 stars, last pushed 7d ago), licensed Apache-2.0. It adds 43 tokens to every session and 799 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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