As title says, latest update of Firefox version 79.0 broke all our bots in production and we are unable to use any selectors other than some headers. UI Explorer seems to not be able to interact with it. We have tried re-installing Plugin, browser and other things to no avail so far. Going to explore rolling back to an older version.
Hope to save you a headache
EDIT: this behavior is with our two main business applications - your mileage may vary! Have not had the chance to test this on other applications as we are working on a fix