Pop-ups that show up for split-second in corner of screen and vanish

Since yesterday or so, I’ve had pop-ups that flash momentarily in the corner of my Chrome browser- not even like 1/4 of a second, and I can never see what they are - and then they vanish instantly, although they appear to be nothing but a blank white pop-up. And today I’ve been mysteriously logged out of YouTube despite not asking to. Does this resemble virus behavior?

Shows up on multiple sites, yeah.

Isn’t it just your ad blocker running a bit slow?

Too much porn surfing

Why is porn always the go to answer for browser problems? Shouldn’t the malware/AV programs take care of that?