Firefox internal & external web-page icons appearing abnormal
Hi, I am currently running FF 91.0.2 on Xubuntu 18.04 and recently icons are appearing abnormally on both Firefox internal web pages such as: about:preferences#privacy (see 1st pic),
as well as on external web pages such as: YouTube https://www.youtube.com/watch?v=1zrg2Vanfco (see 2nd pic)
I have re-installed FF and imported my old profile but no difference. I have tried to restart FF in Troubleshoot mode but it doesn't resolve the problem, what to do?
EDIT: Solution provided by cor-el solved the problem with Firefox internal pages.
The problem with YouTube "new" black-and-white icons seems to be something else as these appear with other browsers too.
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Wšě wotmołwy (2)
Issues with checkboxes can happen if you have set "browser.proton.enabled = false" on the about:config page to disable Proton.
In Firefox 91+ you can no longer disable Proton and revert changes that come with this design via "browser.proton.enabled = false" on the about:config page. Best in Firefox 91 is to set browser.proton.enabled at its default value true as the false setting can cause issues with checkboxes.
In Firefox 91+ you need to use code in userChrome.css to override changes coming with the Proton design.
WARNING: This script is not provided by Mozilla and is not officially supported Creating a userChrome.css file and other ways of customizing Firefox that are not exposed in the interface are there for developers, not end-users. If it were intended for end-users, you would see a menu option or checkbox; you wouldn't have to hack a text file in a hidden location.
What this means is that even though the functionality you want is no longer supported, a third-party has found a way to do it using the CSS file. If it breaks in new versions, you will need to contact the person who provided the script.