Evidence review
What to inspect before changing anything
Start with the delivered website and the real user journey. Record the current state so the team can distinguish an observed problem from an assumption and compare the same surface after deployment.
- 01Enumerate endpoints that emit CORS headers
- 02Test trusted, untrusted and null origins
- 03Check credentialed responses and preflight caching
Implementation
A practical improvement plan
Make the smallest coherent change that solves the observed problem. Keep normal code review, accessibility, security and product checks in the loop instead of optimizing for the scan alone.
- 01Maintain an explicit origin allowlist
- 02Validate the complete Origin value server-side
- 03Limit methods and headers to real client needs
Verification
How to verify the result
Verification should test the intended outcome and the most likely regression. Use the production delivery path whenever headers, caching, rendering or third-party services affect the result.
- 01Send preflights from allowed and hostile origins
- 02Confirm credentials never pair with wildcard origins
- 03Test cache variation by Origin
Common pitfall
A shortcut to avoid
Reflecting any supplied Origin converts a visual allowlist into universal browser access.
Further reading
Primary guidance and references
These sources provide standards, security guidance or the interpretation framework used to keep this guide bounded. Product-specific implementation still requires review in the actual codebase.