Problem

The extract_domain_from_url function in transform.py (lines 98-107) lacks proper input validation and sanitization, potentially causing security vulnerabilities or application crashes when processing malformed URLs.

Location

• File: transform.py
• Lines: 98-107
• Function: extract_domain_from_url

Code Issue

def extract_domain_from_url(url: str) -> str:
    try:
        if "://" in url:
            url = url.split("://")[1]
        domain = url.split("/")[0]
        if domain.startswith("www."):
            domain = domain[4:]
        return domain
    except Exception:
        return ""

The function processes URLs without validating:

• URL format structure
• Malicious input patterns
• Injection attack vectors
• Input length limits

Root Cause

The function assumes all input is valid and only handles basic URL parsing without:

• URL format validation
• Input sanitization
• Security checks for malicious patterns
• Proper error handling for edge cases

Impact

• Severity: Medium-High
• Security Risks:
  • Potential injection attacks through malformed URLs
  • Application crashes from unexpected input patterns
  • Data corruption from invalid URL processing
• Reliability Issues:
  • Silent failures with malformed input
  • Inconsistent behavior across different URL formats

Example Vulnerable Inputs

# Malicious inputs that could cause issues:
extract_domain_from_url("javascript:alert('xss')")
extract_domain_from_url("file:///etc/passwd")
extract_domain_from_url("data:text/html,<script>alert('xss')</script>")
extract_domain_from_url("http://" + "x" * 10000)  # Very long input
extract_domain_from_url("")  # Empty string
extract_domain_from_url(None)  # None input

Proposed Fix

Implement comprehensive input validation:

import re
from urllib.parse import urlparse

def extract_domain_from_url(url: str) -> str:
    if not url or not isinstance(url, str):
        return ""
    
    # Limit input length
    if len(url) > 2048:
        return ""
    
    try:
        # Validate URL format
        parsed = urlparse(url)
        if not parsed.scheme or parsed.scheme not in ['http', 'https']:
            return ""
        
        domain = parsed.netloc
        if domain.startswith("www."):
            domain = domain[4:]
        
        # Validate domain format
        if re.match(r'^[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$', domain):
            return domain
        return ""
    except Exception:
        return ""

Steps to Reproduce

1. Call extract_domain_from_url() with malicious input:

   from transform import extract_domain_from_url
   extract_domain_from_url("javascript:alert('xss')")
   extract_domain_from_url("file:///etc/passwd")

2. Observe potential security issues or unexpected behavior

Labels

• bug
• security
• input-validation
• medium-priority