Open Bug 1869329 Opened 1 year ago Updated 5 days ago

White flashes still appear when privacy.resistFingerprinting is true

Categories

(Core :: Privacy: Anti-Tracking, defect, P3)

defect

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()

UNCONFIRMED

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(Reporter: gaxala1852, Unassigned, NeedInfo)

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(Blocks 1 open bug)

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There's a bug that this bug depends on, all the info related to this issue is in this bug. Though the issue has been resolved, it has not been tested with privacy.resistFingerprinting flag set to true. The issue has not been fixed in such a configuration. Proposed fix: add privacy.resistFingerprinting.websiteAppearancePassthrough flag that would allow Website appearance setting to be passed to the webpage so that it would know it is being loaded in a dark environment

The bug I was referencing is somehow missing from this page: https://bugzilla.mozilla.org/show_bug.cgi?id=1863326

This is not a question for extensions, but for the owners of the component responsible for privacy.resistFingerprinting. Therefore I'm moving the bug there.

Could you provide exact reproduction steps to make it easier for other people to check the behavior?

Component: Developer Outreach → Privacy: Anti-Tracking
Product: WebExtensions → Core
See Also: → 1863326

Steps to reproduce are the same, you only set privacy.resistFingerprinting to true beforehand

You can create an exception for the color scheme with fingerprinting protection:

privacy.resistFingerprinting = false
privacy.fingerprintingProtection = true
privacy.fingerprintingProtection.overrides = +AllTargets,-CSSPrefersColorScheme

+AllTargets should be equivalent to privacy.resistFingerprinting and -CSSPrefersColorScheme avoids all flashes for me with the Dark Reader extension.

Severity: -- → S3
Priority: -- → P3

In Firefox 141 (Win x64) white flashes during page loads occur on some websites regardless of fingerprint protection.

  • Windows theme set dark
  • Browser theme set dark
  • Dark reader set to automatic or extension disabled entirely >> no difference
  • privacy.fingerprintingProtection = true or false >> no difference
  • privacy.fingerprintingProtection.overrides = +AllTargets,-CSSPrefersColorScheme >> no difference

On large(r) page loads, when a site only shows an early load placeholder <html><head></head></html> (or even an early <body> still being built up) without any CSS setting the background, the whole page is rendered white. If you catch the loading process even earlier (before anything has been fetched, connection being initialised) there's only a #document without html element in it, this is also rendered white.
It's easy to catch using the dev tools / browser toolbox with network throttling set to a slower connection.

The user agent stylesheets applied at that time don't contain a background-color, and in its absence it defaults to white.

I understand the white flashing is mainly caused by how websites choose to (pre)load and build up the rendering, but can this be prevented on the browser side?
Could Mozilla/Firefox add a fallback user agent stylesheet background color value depending on the chosen light/dark mode and/or website appearance setting? If the dark mode is active > #000.

Coud you please open a new report referencing Bug 1863326 (and potentially also the current bug 1869329)? This bug is only about white flashing when having privacy.resistFingerprinting enabled which is an unsupported configuration (therefore low priority). Note that this is different from privacy.fingerprintingProtection.

If it is happening without fingerprinting protection (which seems to be a different thing from the one reported in this bug), then it'd be good if the relevant team triages it. Not sure which component fits best, might be good to file in Firefox :: General or Firefox :: Untriaged.

Flags: needinfo?(1rufad7o3)
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