I don't know where to submit screen captures to be viewable by anyone without creating accounts and such but here is a URL to the app the ad in this window is advertising for: https://apps.apple.com/app/id1525556960?mt=12<p>The first screenshot is what I see on my screen, except with a message at the top saying "Mirror My Screen (formerly MKMirror) - Free Download expires soon"
and a "Download on the Mac App Store" button at the bottom.<p>Why isn't there any way to close this window without having to click this button in particular? And to be more clear, I cannot close it with Activity Monitor or Force Quit it in any way.<p>At first, I wasn't sure if it was a browser popup window and clicking anywhere in the window doesn't show me what macOS app this belongs to. For all I knew, it could've been malicious in nature and I wouldn't have known until clicking the button.<p>Finally, this window appeared after installing updates for macOS Catalina, I've mostly avoided going to Big Sur for now.