Starting some time ago (not sure what update it was), my system buttons turned transparent on my Firefox installation. It happens whenever I use any light (white taskbar background, system pages backgrounds, etc.) Firefox full theme, and there are many tabs in the window (the buttons start to glitch as I open more 'live' tabs, then go completely; empty ones don't seem to count). They are still functional, just transparent. The problem is not specific to my main profile, I have reproduced it on clean profile with only a theme installed (so, no addons are involved). It doesn't happen, though, when I: * use any dark theme * use a Firefox Color theme * activate Troubleshoot Mode (obviously, as the themes themselves are not enabled) WTF? Any further ideas to investigate?