Well, give them one star on Firefox Extensions review and move to a different brand of AV. I have 270 days to end of my licence and then i will just move to something less buggy with proper support.
Two days back Kaspersky addon for Firefox started using 40% of my CPU and lag and freeze my whole web browser. There are other people who complain about this bug in Firefox addons reviews.
https://addons.mozilla.org/en-US/firefox/addon/kaspersky-protection-2021/reviews/?score=1