After I updated to the newest Firefox on dec. 16, 2020, my computer began to operate at a terribly slow pace. Not just Firefox, everything. I worked with Apple senior advisors and their engineers to try to isolate what could be wrong. In my Mac activity monitor, the kernel_task was using over 500% of the CPU, even with no browser or application open. After 2 or 3 weeks of checking everything, Apple told me it was Firefox that was causing the slowness. I threw Firefox in the trash but nothing improved. I realized that throwing just the application in the trash did not eliminate all of Firefox, so I reinstalled it and then tried to remove anything related to Firefox from my computer. I’m not sure if I got everything, but the situation stayed the same. I reinstalled Firefox and went through all the solutions that I found on these pages. Nothing has helped. My cpu still shows amazingly high activity even when nothing is open. I cannot figure out what to do and my computer is working so slowly it is essentially useless to me. Has anyone else had this issue? Any suggestions?