Did anyone else get a Safari window after the update with a iCloud page to setup family sharing?

yep, it opened to this page https://setup.icloud.com/family/cacheMugshotMarquee?aaaction... which responds with a HTTP/1.1 400 Bad Request

seems like a bug, weird that it didn't get picked up before GM as it was also noticed during the beta: https://developer.apple.com/forums/thread/712858

Some discussion of it from today, but no definitive answers yet https://forums.macrumors.com/threads/strange-safari-open-tab...

It doesn't happen when you update each beta in a row so it probably wasn't noticed. I didn't get it on my beta machine, just on my work machine.