conducting-api-security-testing

conducting-api-security-testing is a skill for Claude Code, Codex from 26zl/cybersec-toolkit. It costs 99 tokens per session (2,567 once invoked), scanned A, original, MIT.

A guide to testing REST, GraphQL, and gRPC APIs for security problems in login checks, permissions, request limits, input handling, and business rules. An API is the interface that lets software exchange data and actions.

In plain words
What is it for?
Use it to assess API endpoints, microservices, gateways, and third-party integrations with tools such as Burp Suite and Postman during authorized security tests.
Why use it?
It helps uncover ways users could access data or actions they should not, bypass safeguards, or abuse an API’s business logic.

Skill for Claude CodeCodex

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

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

Made for: Claude Code, Codex.

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 conducting-api-security-testing

README.md
[![agentmods](https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/conducting-api-security-testing.svg)](https://agentmods.dev/skills/26zl/cybersec-toolkit/conducting-api-security-testing)
Your own site
<a href="https://agentmods.dev/skills/26zl/cybersec-toolkit/conducting-api-security-testing"><img src="https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/conducting-api-security-testing.svg" alt="Measured on agentmods" height="20"></a>
Per session 99 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,567 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 $0.00099 $0.02567
Opus 5 $0.00049 $0.01283
Sonnet 5 $0.00020 $0.00513
Haiku 4.5 $0.00010 $0.00257

Measured yesterday against content hash d7c01bde6250, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

conducting-api-security-testing 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 yesterday.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/agent.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Origin

Copies of this mod

2 near-identical copies found in the catalogue:

.claude/skills/conducting-api-security-testing/SKILL.md · 196 lines

How it starts

The opening of the file, as written. The whole thing — 196 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Conducting API Security Testing

When to Use

  • Testing API endpoints for authorization flaws, injection vulnerabilities, and business logic bypasses
  • Assessing the security of microservices architecture where APIs are the primary communication method
  • Validating that API gateway protections (rate limiting, authentication, input validation) are properly enforced
  • Testing third-party API integrations for data exposure and insecure configurations
  • Evaluating GraphQL APIs for introspection disclosure, query complexity attacks, and authorization bypasses

Do not use against APIs without written authorization, for load testing or denial-of-service testing unless explicitly scoped, or for testing production APIs that process real financial transactions without safeguards.

Prerequisites

  • API documentation (OpenAPI/Swagger, GraphQL schema, Postman collection) or application access to reverse-engineer the API
  • Burp Suite Professional configured to intercept API traffic with JSON/XML content type handling
  • Postman or Insomnia for organizing and replaying API requests across different authentication contexts
  • Valid API tokens or credentials at multiple privilege levels (unauthenticated, standard user, admin)
  • Target API base URL and version information

Workflow

Step 1: API Discovery and Documentation

Map the complete API attack surface:

  • Import API documentation: Load OpenAPI/Swagger specs into Postman or Burp Suite to catalog all endpoints, methods, parameters, and authentication requirements
  • Reverse-engineer undocumented APIs: Proxy the mobile app or web frontend through Burp Suite and exercise all features to capture API calls. Export the Burp sitemap as the baseline endpoint inventory.
  • GraphQL introspection: Send an introspection query to discover the full schema:
    {"query": "{__schema{types{name,fields{name,args{name,type{name}}}}}}"}
    
  • Endpoint enumeration: Fuzz for hidden API versions (/api/v1/, /api/v2/, /api/internal/), debug endpoints (/api/debug, /api/health, /api/metrics), and administrative endpoints
  • Document authentication mechanisms: Identify if the API uses API keys, OAuth 2.0 Bearer tokens, JWT, session cookies, or mutual TLS

Read the full file on GitHub · 196 lines

Files

What ships with it

3 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. yesterday First seen · 196 lines · 99 tokens per session scan A d7c01bde6250

Subscribe to this mod's changes

conducting-api-security-testing is a skill published in the GitHub repository 26zl/cybersec-toolkit (48 stars, last pushed 2d ago), licensed MIT. It adds 99 tokens to every session and 2,567 once invoked, about $0.0005 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 2026-09-03.

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