I first noticed this bug in Thunderbird, when I was writing an email and only the numbers appeared in a strange font and only in white:
Thought this to be a TB specific problem, but by accident I discovered the same thing in uMatrix (extension) in Firefox.
Cannot upload second screenshot
So it only seems to affect Mozilla programs, in the same extension on a Chromium based browser the numbers were displayed normal.
Any ideas how to fix this?
Operating System: Manjaro Linux
KDE Plasma Version: 5.16.3
KDE Frameworks Version: 5.60.0
Qt Version: 5.13.0
Kernel Version: 5.2.1-1-MANJARO
OS Type: 64-bit
Processors: 4 × Intel® Core™ i7-6600U CPU @ 2.60GHz
Memory: 15,1 GiB of RAM