For a few months I have been having sporadic issues with my cpu running at 100%. I believe Firefox is the culprit. When I open task manager Firefox is running 30 processes with power usage very high. Usually one of the top processes in the drop down is very high. To fix this I have been ending the task of the highest usage process running. In all cases that has brought the cpu down to like 10% and has fixed the issue temporarily. If I'm not at my computer for some time, it will not resolve on it's own. I'm not sure what info you need but will provide. Could this be a bug with the current version of ESR? I have tried the fixes including: Disable/Enable Hardware Acceleration, Enable Strict Tracking Protection, Delete content-prefs.sqlite file, Check Firefox hardware acceleration, Disable resource consuming extensions and themes, etc. I am using Firefox ESR 128.6.0 and have been for years (ESR) Computer: Dell Optiplex 9020 1 tb SSD hard drive Inel Core I7 4790 CPU 32GB RAM AMD Radeon R& 200 series GPU