1857392 - Firefox not detecting locally installed fonts

Status: RESOLVED WONTFIX

(Core :: DOM: Security, defect)

Description

[Tim]

Attachment: Installed Font

I've had a chrome/userContent.css file for a while to change fonts to some that I have locally installed and recently (27/09/2023) it stopped working.

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/119.0

Here's the css:

@-moz-document url-prefix("https://www.twitch.tv") {
    :root {
        --font-base: "Noto Sans" !important;
    }
    .live-time {
        font-family: var(--font-base) !important;
    }
}

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Graphics: Text' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Jonathan Kew [:jfkthame]]

Is this issue specifically in Private Browsing windows, and/or do you have Strict tracking protection enabled in Firefox settings?

If so, this is expected (because allowing the use of arbitrary locally-installed fonts provides websites with a way to "fingerprint" and track your browser).

Comment 3

[Tim]

Okay yeah, you're right. Disabling Enhanced Tracking Protection on the site fixes it. Guess something changed with 119 that makes this a bit more aggressive

Comment 4

[Tim]

Is there maybe a way to turn off just the font blocking for a site? Having to turn off all extra protections for this kind of sucks to be honest

Comment 5

[Jonathan Kew [:jfkthame]]

You can turn off the font blocking part of anti-fingerprinting by setting privacy.fingerprintingProtection.overrides to -FontVisibilityLangPack (note the leading "-") in about:config.

(That would be a global setting; I'm not sure if there's a way to do that just for an individual site.)

Comment 6

[Tim]

That's good enough for me, thanks!

Comment 7

[Tom Ritter [:tjr] (OOTO until April)]

Thank you for the report - we're going to mark it working as intended, but appreciate getting a read on how many people this new behavior affects.