Fingerprinting breaks some fonts on popular sites, behavior returns after new updates
Categories
(Core :: Privacy: Anti-Tracking, defect)
Tracking
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People
(Reporter: lizzard, Unassigned)
References
Details
We have reports from Bug 2000429 that while the fix that landed there was helpful, the broken fonts come back after Firefox version updates in Nightly. This could use further testing to reproduce the issue, see if it's reproducible on the release channel, get us profiler info, and so on.
From the original bug report and comments:
Some fonts are broken on several websites like Facebook or X, where "special" fonts are used. This does happen with the "strict" tracking protection, but not with the "standard" tracking protection. Using the "strict" tracking protection and then setting privacy.fingerprintingProtection to false solves it as well. Enabling the checkboxes to fix major or minor site issues does not help.
The Inspector developer tool shows the following font for the affected text in the broken state:
.SF NS
System Font
The same check if the font works:
.SF NS
System Font
STIX Two Math
STIX Two Math Regular
- For debugging, it might be useful to have the output from system_profiler SPFontsDataType. It will dump the paths to all fonts registered on the system (and might include private information in the form of directory names.)
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Comment 1•9 months ago
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We have reports from Bug 2000429 that while the fix that landed there was helpful,
I am not sure if the fix from bug 2000429 was helpful at all. I initially thought so when I tested a test build where the problem did not occur. But that could be a similar phenomenon to the fact that I was never able to reproduce the problem via mozregression. In "real" Firefox builds, the fix never worked for me.
To copy my observation from the other bug:
The problem can be temporarily resolved by starting in troubleshoot mode. As a result, I can restart Firefox as often as I want, and the problem remains resolved. But after every update of Firefox Nightly, the problem reappears.
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Comment 2•7 months ago
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We also have a problem downstream for Tor Browser with this font.
I found that disabling the GPU process fixes it.
Since I'm not sure is totally related to this bug, I opened Bug 2032466, but you might want to check if changing layers.gpu-process.enabled fixes also your problem.
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Comment 3•3 months ago
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I'm not able to reproduce this bug after new testing on 155.0a1 on macOS 27.0 Beta (26A5388g).
Description
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