Within the last day or so, with no advance warning or notice, video ads have popped up while I'm on the Internet using Firefox. They're all in the lower right hand corner of the screen. I can close the vids, but only after 10 seconds have elapsed. I made no changes to my PC, Firefox, or my A/V software that I use. (Scans of my system show nothing bad or unwelcome.) I've always had the "block pop-ups" box, among other related settings, checked on Firefox. None of that seems to be making a difference, because as I said, this annoying crap just started.
This happens regardless of the site I am visiting. In the time it took me to come to this forum and post this, two of these damn ads came on. In addition, a large pop-up box about Seinfeld appeared.
Anyone else experience this or know how to fix this?