I thought I'd post it here for other people to find. I run Linux Mint (64 bit) so this may effect Ubuntu as well and potentially other distributions. After the update to version 89 Firefox was COMPLETELY transparent. I saw more of the background than I did of the browser or the websites. After doing some digging around I found I had to enable layers.acceleration.disabled in config:about. To do this open Firefox and in the address bar type config:about Do a search for layers.acceleration.disabled Double click it to enable it Close firefox and re-open it to verify your transparency is gone. I hope this helps someone.