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Audit for preventing mismatched mime types (x-nosniff)

See original GitHub issue

Provide the steps to reproduce

Run LH on https://developers.google.com/speed/pagespeed/insights
Audit a page which set Content-Type: image/webp on jpg and/or png images

What is the current behavior?

Page passes Serve images in next-gen formats test even though it doesn’t serve images in next-gen formats
Pages which deliver jpg and png images with Content-Type: image/webp get better results

What is the expected behavior?

Audit detects jpg or png images with Content-Type: image/webp are no next-gen formats (e.g. check if the file extension of those images is webp)
Consider adding penalty points in ranking at pages which deliver no next-gen images but cheat by delivering images with a wrong Content-Type

Issue Analytics

State:
Created 4 years ago
Comments:9 (4 by maintainers)

Top GitHub Comments

1reaction

patrickhulcecommented, Jun 25, 2019

We’ve decided this is best solved by an audit that flags requests without x-nosniff. If anyone would like to write this complete audit proposal, be our guest 😃

1reaction

patrickhulcecommented, Jun 17, 2019

1 and 2 are the options I prefer 😃

I would be against 3 for the same reason we filter out other explicit actions against our advice. If you’ve taken the time to move to WebP and you wanted a quality setting higher than our threshold, just go for it, we shouldn’t bother.

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