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pentest-client-advanced

Advanced client-side attacks — CORS misconfiguration, WebSocket security, clickjacking, postMessage abuse, CSS injection, and browser storage vulnerabilities.

Skill by jd-opensource

IndexedApache-2.0★ 315
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Works with Claude Code, Claude apps, Codex, Cursor, Gemini CLI, GitHub Copilot, VS Code, OpenCode, Goose, Windsurf. Read the repository before you give any tool access to your data.

npx agentmarket install skill/jd-opensource-pentest-client-advanced

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About

Advanced client-side attacks — CORS misconfiguration, WebSocket security, clickjacking, postMessage abuse, CSS injection, and browser storage vulnerabilities.

Use cases: frontend, security

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Permissions

What this skill can do and what it asks for, from its SKILL.md. Checked Oct 25, 2026.

Tools
No tools found
Secrets
None asked for
Install scripts
None found

Network hosts it talks to 1

  • codeload.github.com · found in install command

Files it touches

  • ~/.claude/skills/pentest-client-advanced

What's inside

Skill name
pentest-client-advanced
Description
Advanced client-side attacks — CORS misconfiguration, WebSocket security, clickjacking, postMessage abuse, CSS injection, and browser storage vulnerabilities.
License
Apache-2.0
Instructions
54 lines in SKILL.md · view on GitHub

Files (3)

  • SKILL.md
  • tools.md · references/
  • workflows.md · references/

SKILL.md (first lines)

# Pentest Client Advanced

## Purpose
Test advanced client-side attack surfaces beyond XSS. Six WSTG-CLNT items remain unchecked in Shannon's pipeline — these are distinct attack classes requiring different methodology than taint analysis.

## Prerequisites

### Authorization Requirements
- **Written authorization** with client-side testing scope
- **Test domains** for hosting PoC HTML pages (attacker-controlled origin)
- **Browser testing environment** with DevTools access
- **Target user simulation** — ability to test cross-origin interactions

### Environment Setup
- Modern browser with DevTools (Chrome/Firefox)
- Burp Suite for intercepting WebSocket and cross-origin traffic
- Local HTTP server for hosting PoC pages (python -m http.server)
- Playwright for automated browser-based attack verification

## Core Workflow
1. **CORS Misconfiguration**: Test reflected Origin in ACAO header, null origin bypass, subdomain wildcard abuse, credential leakage via cross-origin requests (WSTG-CLNT-07).
2. **WebSocket Security**: Missing auth on WS upgrade, CSWSH (Cross-Site WebSocket Hijacking), injection through WS messages, missing origin validation (WSTG-CLNT-10).
3. **Clickjacking**: Missing X-Frame-Options / CSP frame-ancestors, UI redressing, drag-and-drop hijacking, multi-step clickjacking chains (WSTG-CLNT-09).
4. **postMessage Abuse**: Missing origin validation in message handlers, DOM manipulation via cross-origin messages, prototype pollution through postMessage (WSTG-CLNT-11).
5. **CSS Injection**: Data exfiltration via CSS attribute selectors + background-image, CSS-based keylogging, style injection for UI manipulation (WSTG-CLNT-05).
6. **Client-Side Storage**: Sensitive data in localStorage/sessionStorage, IndexedDB exposure, service worker cache poisoning (WSTG-CLNT-06).
7. **PoC Construction**: Build HTML pages demonstrating each attack with real impact.

## WSTG Coverage

| WSTG ID | Test Name | Status |
|---------|-----------|--------|
| WSTG-CLNT-05 | CSS Injection | ✅ |
| WSTG-CLNT-06 | Client-Side Resource Manipulation | ✅ |
| WSTG-CLNT-07 | Cross-Origin Resource Sharing | ✅ |
| WSTG-CLNT-09 | Clickjacking | ✅ |
| WSTG-CLNT-10 | WebSocket Testing | ✅ |
| WSTG-CLNT-11 | Web Messaging | ✅ |

## Tool Categories

| Category | Tools | Purpose |
|----------|-------|---------|
| CORS Testing | CORScanner, curl, custom PoC pages | CORS misconfiguration detection |
| WebSocket | websocket-client (Python), Burp WS | WebSocket hijacking and injection |
| Clickjacking | custom HTML iframes, Playwright | UI redressing PoC construction |
| Browser Automation | Playwright, Puppeteer | Automated client-side attack verification |
| Storage Analysis | Browser DevTools, custom JS | localStorage/IndexedDB inspection |

## References
- `references/tools.md` - Tool function signatures and parameters
- `references/workflows.md` - Attack pattern definitions and test vectors

From jd-opensource/JoySafeter, Apache-2.0.

More from jd-opensource/JoySafeter

Signals

Stars
315
Forks
56
Open issues
17
Last commit (this folder)
Feb 11, 2026 (8 months ago)
Last release
Jul 2, 2026 (3 months ago)

From GitHub (fetched Oct 24, 2026).

Details

License
Apache-2.0
First seen
Oct 24, 2026
Last checked
Oct 24, 2026

More from jd-opensource

Cite this page

pentest-client-advanced skill. Agent Mart. https://agentmart.dev/skills/jd-opensource-pentest-client-advanced (last updated 2026-10-24)