# Broken Authentication

> 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

- Skill: `ranbot-ai/broken-authentication` (Agent Skill)
- Install (CLI): `npx skillmds add ranbot-ai/broken-authentication`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ranbot-ai/broken-authentication/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- Author: ranbot-ai (https://skillmd.com/u/ranbot-ai)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/ranbot-ai/broken-authentication

---



> **⚠️ AUTHORIZED USE ONLY**
> This skill is for educational purposes or authorized security assessments only.
> You must have explicit, written permission from the system owner before using this tool.
> Misuse of this tool is illegal and strictly prohibited.

> **Mandatory confirmation gate**
> Before running any command that probes, exploits, changes, persists on, extracts data from, or attempts credential access against a target:
> 1. Ask the user to state the exact target URL, IP, account, or resource.
> 2. Ask the user to confirm written authorization and the permitted scope.
> 3. Show the exact command(s) and explain their expected effect.
> 4. Wait for explicit confirmation in the current conversation.
>
> Without that confirmation, remain read-only and provide defensive guidance only. Prefer a sandbox, disposable VM, or controlled lab.

# 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:

```bash
# Test minimum length (a, ab, abcdefgh)
# Test complexity (password, password1, Password1!)
# Test common weak passwords (123456, password, qwerty, admin)
# Test username as password (admin/admin, test/test)
```

Document policy gaps: Minimum length <8, no complexity, common passwords allowed, username as password.

### Phase 3: Credential Enumeration

Test for username enumeration vulnerabilities:

```bash
# Compare responses for valid vs invalid usernames
# Invalid: "Invalid username" vs Valid: "Invalid password"
# Check timing differences, response codes, registration messages
```

# Password reset
"Email sent if account exists" (secure)
"No account with that email" (leaks info)

# API responses
{"error": "user_not_found"}
{"error": "invalid_password"}
```

### Phase 4: Brute Force Testing

Test account lockout and rate limiting:

```bash
# Using Hydra for form-based auth
hydra -l admin -P /usr/share/wordlists/rockyou.txt \
  target.com http-post-form \
  "/login:username=^USER^&password=^PASS^:Invalid credentials"

# Using Burp Intruder
1. Capture login request
2. Send to Intruder
3. Set payload positions on password field
4. Load wordlist
5. Start attack
6. Analyze response lengths/codes
```

Check for protections:

```bash
# Account lockout
- After how many attempts?
- Duration of lockout?
- Lockout notification?

# Rate limiting
- Requests per minute limit?
- IP-based or account-based?
- Bypass via headers (X-Forwarded-For)?

# CAPTCHA
- After failed attempts?
- Easily bypassable?
```

### Phase 5: Credential Stuffing

Test with known breached credentials:

```bash
# Credential stuffing differs from brute force
# Uses known email:password pairs from breaches

# Using Burp Intruder with Pitchfork attack
1. Set username and password as positions
2. Load email list as payload 1
3. Load password list as payload 2 (matched pairs)
4. Analyze for successful logins

# Detection evasion
- Slow request rate
- Rotate source IPs
- Randomize user agents
- Add delays between attempts
```

### Phase 6: Session Management Testing

Analyze session token security:

```bash
# Capture session cookie
Cookie: SESSIONID=abc123def456

# Test toke