"CoreServicesUIAgent" "Verifying "Microsoft Outlook""

As I was using Google Chrome on my Macbook Air [macOS Big Sur Version 11.2.1(20D74)], a new window appeared over everything I was doing, with a progress bar reading "Verifying Microsoft Outlook".

One small problem: I do not use, and have never opened, Microsoft Outlook on this computer.

The window only has a yellow "minimize" button by no red x "close" button. When I minimized the window, the icon on the dock read "CoreServicesUIAgent".

According to "Force Quit" the only application open is Google Chrome and according to Finder, "CoreServicesUIAgent" does not appear to exist anywhere on my computer.

MalWareBytes shows nothing.

The progress bar on the "Verifying Microsoft Outlook" window has been entirely blue for nearly an hour in spite of me repeatedly clicking the "x" at the end, which ordinarily stands for "cancel"

I have already deleted Microsoft Outlook from my computer just to be sure.

What is "CoreServicesUIAgent", what is it "verifying" and why, and how can I get it to stop and close?