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.
- 01Check X-Content-Type-Options on HTML and assets
- 02Find scripts or styles with incorrect content types
- 03Review file-download and user-upload responses
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.
- 01Send nosniff consistently
- 02Correct Content-Type values at the server or CDN
- 03Separate untrusted downloads from executable content
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.
- 01Load scripts, styles and downloads in target browsers
- 02Inspect response headers after CDN caching
- 03Verify uploaded files cannot be interpreted as active content
Common pitfall
A shortcut to avoid
Adding nosniff before correcting MIME types can expose delivery mistakes by breaking assets in production.
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.