I recently had a fake warning page pop up, saying I had malware and should call "Microsoft". I didn't. Also when I click on a link, I often get not only what I expect, but an additional tab to some additional site. I did a full scan with Defender. I ran a few free antivirus programs. I finally downloaded and run a full check with McAfee. Nothing found in any of my scans. No idea what to try next......