fuzzing-apis

This skill enables Claude to perform automated fuzz testing on APIs to discover vulnerabilities, crashes, and unexpected behavior. It leverages malformed inputs, boundary values, and random payloads to generate comprehensive fuzz test suites. Use this skill when you need to identify potential SQL injection, XSS, command injection vulnerabilities, input validation failures, and edge cases in APIs. Trigger this skill by requesting fuzz testing, vulnerability scanning, or security analysis of an API. The skill is invoked using the `/fuzz-api` command.

25 stars

byComeOnOliver

View on GitHub Installation ↓

Best use case

fuzzing-apis is best used when you need a repeatable AI agent workflow instead of a one-off prompt.

Teams using fuzzing-apis should expect a more consistent output, faster repeated execution, less prompt rewriting.

When to use this skill

You want a reusable workflow that can be run more than once with consistent structure.

When not to use this skill

You only need a quick one-off answer and do not need a reusable workflow.
You cannot install or maintain the underlying files, dependencies, or repository context.

Installation

Claude Code / Cursor / Codex

$curl -o ~/.claude/skills/api-fuzzer/SKILL.md --create-dirs "https://raw.githubusercontent.com/ComeOnOliver/skillshub/main/skills/jeremylongshore/claude-code-plugins-plus-skills/api-fuzzer/SKILL.md"

Manual Installation

Download SKILL.md from GitHub
Place it in .claude/skills/api-fuzzer/SKILL.md inside your project
Restart your AI agent — it will auto-discover the skill

How fuzzing-apis Compares

Feature / Agent	fuzzing-apis	Standard Approach
Platform Support	Not specified	Limited / Varies
Context Awareness	High	Baseline
Installation Complexity	Unknown	N/A

Frequently Asked Questions

What does this skill do?

Where can I find the source code?

You can find the source code on GitHub using the link provided at the top of the page.

SKILL.md Source

## Overview

This skill allows Claude to conduct automated fuzz testing on REST APIs. It identifies potential security flaws and robustness issues by injecting various malformed inputs, boundary values, and random data.

## How It Works

1. **Input Generation**: The skill generates a diverse set of test inputs, including malformed data, boundary values, and random payloads.
2. **API Interaction**: It sends these inputs to the specified API endpoints.
3. **Result Analysis**: It analyzes the API's responses and behavior to identify vulnerabilities, crashes, and unexpected results, such as SQL injection errors or XSS vulnerabilities.

## When to Use This Skill

This skill activates when you need to:
- Identify potential security vulnerabilities in an API.
- Test the robustness of an API against unexpected inputs.
- Ensure proper input validation is implemented in an API.

## Examples

### Example 1: Discovering SQL Injection Vulnerability

User request: "Fuzz test the /users endpoint for SQL injection vulnerabilities."

The skill will:
1. Generate SQL injection payloads.
2. Send these payloads to the /users endpoint.
3. Analyze the API's responses for SQL errors or unexpected behavior indicating a SQL injection vulnerability.

### Example 2: Testing Input Validation

User request: "Fuzz test the /products endpoint to check for input validation issues with price and quantity parameters."

The skill will:
1. Generate malformed inputs for price and quantity (e.g., negative values, extremely large numbers, non-numeric characters).
2. Send these inputs to the /products endpoint.
3. Analyze the API's responses for errors or unexpected behavior, indicating input validation failures.

## Best Practices

- **Specificity**: Be specific about the API endpoint or parameters you want to fuzz.
- **Context**: Provide context about the expected behavior of the API.
- **Iteration**: Run multiple fuzzing sessions with different input sets for thorough testing.

## Integration

This skill can be used in conjunction with other security analysis tools to provide a more comprehensive assessment of an API's security posture. It can also be integrated into a CI/CD pipeline to automate security testing.

Related Skills

versioning-apis

from ComeOnOliver/skillshub

Implement API versioning with backward compatibility, deprecation notices, and migration paths. Use when managing API versions and backward compatibility. Trigger with phrases like "version the API", "manage API versions", or "handle API versioning".

throttling-apis

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Implement API throttling policies to protect backend services from overload. Use when controlling API request rates. Trigger with phrases like "throttle API", "control request rate", or "add throttling".

rate-limiting-apis

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Implement sophisticated rate limiting with sliding windows, token buckets, and quotas. Use when protecting APIs from excessive requests. Trigger with phrases like "add rate limiting", "limit API requests", or "implement rate limits".

monitoring-apis

from ComeOnOliver/skillshub

Build real-time API monitoring dashboards with metrics, alerts, and health checks. Use when tracking API health and performance metrics. Trigger with phrases like "monitor the API", "add API metrics", or "setup API monitoring".

mocking-apis

from ComeOnOliver/skillshub

Generate mock API servers for testing and development with realistic response data. Use when creating mock APIs for development and testing. Trigger with phrases like "create mock API", "generate API mock", or "setup mock server".

migrating-apis

from ComeOnOliver/skillshub

Implement API migrations between versions, platforms, or frameworks with minimal downtime. Use when upgrading APIs between versions. Trigger with phrases like "migrate the API", "upgrade API version", or "migrate to new API".

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from ComeOnOliver/skillshub

Execute comprehensive load and stress testing to validate API performance and scalability. Use when validating API performance under load. Trigger with phrases like "load test the API", "stress test API", or "benchmark API performance".

generating-rest-apis

from ComeOnOliver/skillshub

Generate complete REST API implementations from OpenAPI specifications or database schemas. Use when generating RESTful API implementations. Trigger with phrases like "generate REST API", "create RESTful API", or "build REST endpoints".

Writing Fuzzing Harnesses

from ComeOnOliver/skillshub

A fuzzing harness is the entrypoint function that receives random data from the fuzzer and routes it to your system under test (SUT). The quality of your harness directly determines which code paths get exercised and whether critical bugs are found. A poorly written harness can miss entire subsystems or produce non-reproducible crashes.

Overcoming Fuzzing Obstacles

from ComeOnOliver/skillshub

Codebases often contain anti-fuzzing patterns that prevent effective coverage. Checksums, global state (like time-seeded PRNGs), and validation checks can block the fuzzer from exploring deeper code paths. This technique shows how to patch your System Under Test (SUT) to bypass these obstacles during fuzzing while preserving production behavior.

Fuzzing Dictionary

from ComeOnOliver/skillshub

A fuzzing dictionary provides domain-specific tokens to guide the fuzzer toward interesting inputs. Instead of purely random mutations, the fuzzer incorporates known keywords, magic numbers, protocol commands, and format-specific strings that are more likely to reach deeper code paths in parsers, protocol handlers, and file format processors.

api-fuzzing-for-bug-bounty

from ComeOnOliver/skillshub

This skill should be used when the user asks to "test API security", "fuzz APIs", "find IDOR vulnerabilities", "test REST API", "test GraphQL", "API penetration testing", "bug bounty API testing", or needs guidance on API security assessment techniques.