I ran a SmartScan this morning and it warned me that Firefox hadn’t updated itself. I had that resolved and downloaded a new Firefox installation just to be sure. After rebooting, Avast informed me that not all the Firefox files had been cleaned out, should it delete them. Thinking it meant files relevant to the old version, I told it to go ahead. It promptly deleted Firefox altogether.
I had to create an exception for it to install Opera, which I’m using at the moment. Is the current Avast only friendly to IE11? I’m running Windows 8.1, being unwilling to upgrade to Windows 10 just yet.