Thanks to Steve Gibsons ‘Security Now!’ show notes available at https://www.grc.com/sn/sn-1050-notes.pdf for reporting, on page 3, that Chrome and Microsoft Edge have introduced what they call a help popup designed to spot and block full screen popups and phony warnings.
Steve mentions that it is very memory intensive and can be turned off, but if you use these browsers, perhaps you should consider whether you want it turned on or not. The balance is likely to be safety versus browser performance.