(outdated) Firefox 72 allows for MIME sniffing on top-level documents when no Content Type is set #25371
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caugner
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Dec 11, 2024
| "version_added": "50" | ||
| "version_added": "50", | ||
| "impl_url": "https://bugzil.la/1591932", | ||
| "notes": "Since version 72, Content Type sniffing is enabled on top-level documents that have no `Content-Type`, even when `X-Content-Type-Options: nosniff` is set." |
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In other words: Firefox ignores the X-Content-Type-Options header if the response has no Content-Type header?
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Yes, you should be setting a Content-Type if you're saying X-Content-Type-Options: nosniff.
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Would this be accurate and easier to understand?
Suggested change
| "notes": "Since version 72, Content Type sniffing is enabled on top-level documents that have no `Content-Type`, even when `X-Content-Type-Options: nosniff` is set." | |
| "notes": "Firefox 72 and later ignores the header on top-level documents that have no `Content-Type` set." |
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Oh, after digging, this was reverted in Fx 75, https://bugzilla.mozilla.org/show_bug.cgi?id=1594766
So from 75 onwards, it's as follows:
/*
* If we did not get a useful Content-Type from the server
* but also have sniffing disabled, just determine whether
* to use text/plain or octetstream and log an error to the Console
*/
So X-Content-Type-Options: nosniff is respected.
I think we can close this as there's nothing really useful to add here.
bsmth
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edit: See #25371 (comment)
Summary
Adding impl_ulrs for some HTTP features. These were documented in MDN content prose, and removed in recent PRs.
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