I forgot to mention...the reason I scanned for viruses in the first place is because the above linked Firefox article mentioned that there are viruses out there specifically targeting the Firefox browser. Defender will not let me easily look at a detailed log so I can get the virus names...I get prompted with "Do You Want To Allow This Device To Make Changes To Your Computer?" message when I try to drill down to the specific virus that was removed. I'm not opening another can of worms.
I have Defender set to scan "periodically" but I have never been aware of it scanning nor received any notifications of scan results. I always just "assume" that no news is good news. I always click OK on the "... make changes to your computer" message because it usually follows some action I made, like installing or downloading something.
Defender scans my system every day...but it's the Quick Scan, which found nothing. Only the Full Scan picked these 2 up. That "Make Changes" message came when I clicked where it said "Threat Quarantined" (but no names) in Protection History.