Background: Firefox added the Canvas Permission Prompt, people turned it on. They discovered that blog.mozilla.com was triggering it, investigated. Tracked it down to Wordpress, by default, using canvas to figure out if the user has emoji support. Fairly innocuous use, not for tracking.
Wordpress would like to detect Tor Browser so it doesn't perform the check and therefore doesn't pop the prompt. This would significantly reduce the number of prompts Tor Browser users are seeing. The (old) ticket is here: https://trac.torproject.org/projects/tor/ticket/18195
Other links: Original WP ticket: https://core.trac.wordpress.org/ticket/32138 Mozilla Ticket: https://bugzilla.mozilla.org/show_bug.cgi?id=1413182 New WP Ticket: https://core.trac.wordpress.org/ticket/42428
Is this something TB would take as a patch?
-tom
PS: Unless FF with privacy.resistFingerprinting identified itself as Tor Browser, this wouldn't help FF, just TB. But maybe FF _should_ identify itself as TB if TB starts identifying itself as TB?