# Broken Authentication

Should be used when the user asks to "test for broken authentication vulnerabilities"...

- Repository: https://github.com/zebbern/claude-code-guide (4691 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add zebbern/claude-code-guide --skill broken-authentication -g -a claude-code -y`
Codex: `npx skills add zebbern/claude-code-guide --skill broken-authentication -g -a codex -y`
Cursor: `npx skills add zebbern/claude-code-guide --skill broken-authentication -g -a cursor -y`
Gemini CLI: `npx skills add zebbern/claude-code-guide --skill broken-authentication -g -a gemini-cli -y`

## Description

This skill should be used when the user asks to "test for broken authentication vulnerabilities", "assess session management security", "perform credential stuffing tests", "evaluate password policies", "test for session fixation", or "identify authentication bypass flaws". It provides comprehensive techniques for identifying authentication and session management weaknesses in web applications.

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

# Broken Authentication Testing

## Purpose

Identify and exploit authentication and session management vulnerabilities in web applications. Broken authentication consistently ranks in the OWASP Top 10 and can lead to account takeover, identity theft, and unauthorized access to sensitive systems. This skill covers testing methodologies for password policies, session handling, multi-factor authentication, and credential management.

## Prerequisites

### Required Knowledge
- HTTP protocol and session mechanisms
- Authentication types (SFA, 2FA, MFA)
- Cookie and token handling
- Common authentication frameworks

### Required Tools
- Burp Suite Professional or Community
- Hydra or similar brute-force tools
- Custom wordlists for credential testing
- Browser developer tools

### Required Access
- Target application URL
- Test account credentials
- Written authorization for testing

## Outputs and Deliverables

1. **Authentication Assessment Report** - Document all identified vulnerabilities
2. **Credential Testing Results** - Brute-force and dictionary attack outcomes
3. **Session Security Analysis** - Token randomness and timeout evaluation
4. **Remediation Recommendations** - Security hardening guidance

## Core Workflow

### Phase 1: Authentication Mechanism Analysis

Understand the application's authentication architecture:

```
# Identify authentication type
- Password-based (forms, basic auth, digest)
- Token-based (JWT, OAuth, API keys)
- Certificate-based (mutual TLS)
- Multi-factor (SMS, TOTP, hardware tokens)

# Map authentication endpoints
/login, /signin, /authenticate
/register, /signup
/forgot-password, /reset-password
/logout, /signout
/api/auth/*, /oauth/*
```

Capture and analyze authentication requests:

```http
POST /login HTTP/1.1
Host: target.com
Content-Type: application/x-www-form-urlencoded

username=test&password=test123
```

### Phase 2: Password Policy Testing

Evaluate password requirements and enforcement:

The rest: https://github.com/zebbern/claude-code-guide/blob/HEAD/skills/broken-authentication/SKILL.md