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prototype-pollution

Detect prototype pollution vulnerabilities in JavaScript stacks via injection probes.

96|1|Updated Jun 4, 2026
Search Tags:#penetration testing#vulnerability testing#client-side security#prototype pollution#javascript security#node.js security
One-click install
npx skills add https://github.com/langbyyi/CyberStrikeAI-SRC --skill prototype-pollution-langbyyi
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: prototype-pollution
Source: https://github.com/langbyyi/CyberStrikeAI-SRC/tree/main/skills/prototype-pollution
Command: npx skills add https://github.com/langbyyi/CyberStrikeAI-SRC --skill prototype-pollution-langbyyi

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

This Skill addresses the risk of prototype pollution vulnerabilities in JavaScript applications, which occur when untrusted user input is merged into nested objects without proper sanitization, allowing attackers to modify shared prototype properties and trigger remote code execution, denial of service, or application logic bypasses.

Core Features & Use Cases

  • Dual-scope detection: Covers both client-side (URL fragments, DOM injection) and server-side (Express, qs parser, Node.js) prototype pollution attack vectors.
  • Exploitation guidance: Includes gadget chains for common targets like EJS templates, Node.js child_process, and CORS misconfigurations to demonstrate real-world impact.
  • Use case: Security testers can use this Skill during authorized penetration tests to assess JavaScript web apps, Node.js APIs, and frontend frameworks for prototype pollution risks, with a built-in decision tree to streamline testing workflows.

Quick Start

Use the prototype-pollution skill to test a target Node.js Express API endpoint for server-side prototype pollution by sending crafted JSON payloads and checking for persistent global side effects in subsequent clean requests.

Frequently Asked Questions about prototype-pollution

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How does prototype pollution work in JavaScript applications?▼

Prototype pollution occurs when untrusted user input is merged into nested JavaScript objects without sanitization, modifying shared prototype properties to trigger remote code execution or logic bypasses.

How do I test for prototype pollution in a Node.js Express API?▼

To test a Node.js Express API for prototype pollution, send crafted JSON payloads containing __proto__ or constructor.prototype injection vectors and check subsequent clean requests for persistent global side effects.

Can prototype pollution affect client-side browser environments and frontend frameworks?▼

Yes, client-side prototype pollution affects browser environments through URL fragments and DOM injection, allowing attackers to manipulate frontend frameworks processing untrusted query parameters.

What are common gadget chains for exploiting prototype pollution vulnerabilities?▼

Common prototype pollution exploitation gadget chains target EJS templates and Node.js child_process modules to achieve remote code execution, while CORS misconfigurations demonstrate real-world application impact.

Which JavaScript parsers are vulnerable to prototype pollution attacks?▼

JavaScript parsers like qs, body-parser, lodash.merge, and deep-extend are vulnerable to prototype pollution when processing untrusted query parameters, JSON bodies, or configuration inputs without proper sanitization.

What is the best way to identify prototype pollution flaws during penetration testing?▼

The best way to identify prototype pollution flaws during penetration testing is using a decision tree workflow that applies detection probes for __proto__ and constructor.prototype injection vectors across JavaScript stacks.

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