Today, using the latest release version of Firefox on Win10, I tried to go to Facebook. Instead, my screen was taken over by a site claiming to be “Microsoft Official Support”, which launched several boxes claiming that there was an unknown error on my machine, and that my “winkey47” had gone bad, so that I needed to call a technician at 855-402-8150 in order to get instructions on how to fix my machine. It was not possible to close any of the boxes or messages. Had to use Task Manager to close Firefox. Firefox history showed that immediately after asking it to go to Facebook, I was taken to prospervolumethrive.com/jf1l3mdf/, and immediately thereafter my machine loaded about twenty sites all with the same initial URL of microsoft.com-winkey47.info. These are presumably the source of all the boxes that appeared on my screen. The real Microsoft support site does not have that sort of URL.
I ran an Avast boot scan that turned up nothing. I ran the Avast browser add-on scan that turned up nothing. I looked at my list of add-ons and extensions and found nothing that I did not recognize.
Later, after clearing recent cookies and cache, I tried visiting Facebook again, using Firefox, and Edge, but nothing unusual happened.
Anyone know what is going on here?