Not today but, that has happened to me 3 or so times over the years. Either Apple has a problems, or someone may have been trying to hack your account and it triggered a reset by Apple.
Yeah, had all of my devices forced to sign out, had my account locked and required to do a password change. Been speaking with others on Twitter who had the same thing just happen. I wonder what's going on.
I wonder if the password requirements have changed recently [edit: nope, they haven’t changed]. I read on an Apple discussion this happened after a user upgraded iCloud storage, but that seems a bit random.
Macrumors had a story about this in 2018. The users were kicked out and forced to reset the password for security reasons:
Apple appears to have locked a select group of users out of their Apple ID accounts over the past 20 hours or so, with no clear indication yet as to...
If you’re all on iOS 14 or have been, it has to do with Apple’s servers. Some other issues include icloud photos and messages in the cloud. In my case, I can’t delete and disable messages in the cloud. I get the download messages loop. Several senior advisors have told me and others that the fix is coming in a future update.