The in-laws' computer had a similar issue, in that it was getting a bunch of shady popups piling up from the bottom right corner (Windows notification popups),

The in-laws' computer had a similar issue, in that it was getting a bunch of shady popups piling up from the bottom right corner (Windows notification popups), where eventually it would cover 1/4 of the screen. Tracked it down to Chrome, and sites that were allowed push notifications. Took a minute to purge the allow list, turn off the prompt to ask for notification permissions (non-technical people tend to click on "ok" or "yes" on most dialog boxes). But overall much easier than the old days of having to manually remove malware and/or reinstall the OS.