Prompt from iCloud saying that verification code has been sent to my apple devices

I'm running Windows 10 and I'm getting an iCloud.com popup telling me that a verification code has been sent to my apple devices. I input the code and the same prompt keeps coming back. I understand this has to do with non-Apple apps needing a separate password. I click on manage appleid and go to manage app-specific passwords but I don't know which specific app wants the password. It could be a lot of different things. How do I know which apps are looking for a password specific to that app?