Happened to me last night. I got a push notification on my watch that I needed to update my iCloud password. I thought that this isn't right, so I went to my phone and MacBook. Same thing, those devices said I needed to change my password. So I figured someone has my @iCloud email address and tried to login. I do have hardware keys setup, so wasn't terribly worried.

But none the less, I liked my old password and had to change to something else.