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Abhinav Singwal
Abhinav Singwal

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CORS Misconfiguration Scanner: A Powerful Tool for Web Security Testing

#cors #corsy #crossorigin #cybersecurity

Cross-Origin Resource Sharing (CORS) is a critical security mechanism that allows web applications to request resources from different domains. However, misconfigured CORS policies can expose your application to serious security vulnerabilities. Today, I'm excited to share a powerful tool called cors - a dedicated CORS misconfiguration scanner that helps security professionals and developers identify and fix these vulnerabilities.

What is CORS Misconfiguration Scanner?

CORS - Cross-Origin Resource Sharing (CORS) is a critical security mechanism that allows web applications to request resources from different domains.

GitHub: https://github.com/yogsec/cors

The cors tool is a fast, efficient command-line utility designed to detect CORS misconfigurations in web applications. Created by yogsec, this open-source tool helps you identify potential security loopholes before attackers can exploit them.

Key Features

  • Single URL Scanning: Test individual endpoints quickly
  • Bulk URL Scanning: Process multiple URLs from a wordlist
  • Multi-threaded Support: Configure concurrent threads for faster scanning
  • Custom Output: Save results to a file for later analysis
  • User-Friendly Interface: Clear output with vulnerability indicators

Understanding CORS Vulnerabilities

The tool checks for common CORS misconfigurations including:

  • Wildcard (*) in ACAO: Server accepts requests from any origin
  • Origin Reflection: Server echoes back the Origin header
  • Unsafe HTTP Methods: Allow dangerous methods like PUT/DELETE
  • Wildcard in ACAH: All headers are permitted
  • Credentials Enabled: Server allows sending credentials with requests

Installation Guide

Automatic Installation (Recommended) 

git clone https://github.com/yogsec/cors
cd cors
sudo chmod +x install.sh
sudo ./install.sh
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Manual Installation 

git clone https://github.com/yogsec/cors
cd cors
chmod +x cors
sudo cp cors /usr/local/bin/
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Verify Installation 

cors -v
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Expected output: cors version: 1.0

How to Use

Basic Syntax 

cors [OPTIONS]
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Usage Examples

1. Scan a Single URL 

cors -u https://example.com
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Output example:

[*] Checking: https://example.com
[!] https://example.com - Reflects origin in ACAO
[!] https://example.com - Credentials enabled
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2. Scan Multiple URLs

Create a file urls.txt:

https://example.com
https://test.com/api
https://target.com
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Run the scan:

cors -w urls.txt
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3. Save Results to a File 

cors -w urls.txt -o results.txt
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4. Increase Scanning Speed 

cors -w urls.txt -c 20
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5. Combine Multiple Options 

cors -w urls.txt -o vulnerable.txt -c 30
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Get Involved

Why This Tool Matters

In today's web application landscape, CORS misconfigurations are among the most common and dangerous security vulnerabilities. This tool provides:

  1. Quick Identification: Rapidly detect potential CORS issues
  2. Automated Testing: Streamline your security testing process
  3. Comprehensive Coverage: Test multiple URLs and configurations
  4. Developer-Friendly: Easy to use with clear output

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