How to Use the CORS Misconfiguration & Policy Tester
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1
Select Access-Control-Allow-Origin setting: Wildcard (*), Specific Domain, or Reflect Origin.
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2
Toggle Access-Control-Allow-Credentials (true/false).
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3
Review security verdict: alerts on critical vulnerabilities (like Wildcard + Credentials).
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4
Copy hardened Nginx, Apache, or Express.js CORS middleware.
Practical Example & Use Case
Common Real-World Scenario
Verifying that an API does not expose sensitive authenticated session cookies to unauthorized third-party domains via CORS.
Technical Notes & Limitations
Browser Engine Architecture
Simulates W3C Fetch CORS specification logic directly inside the browser.
Frequently Asked Questions
Why is `*` with credentials dangerous?
Browsers strictly forbid `Access-Control-Allow-Origin: *` when credentials are included because it would allow any website to steal authenticated data.