After updates about 20 minutes ago, ran into an issue on reboot where passwords (including root) were invalid or reset, and the users accounts were expired, unable to "unexpire" by any of the usual means.
Was able to reset root using "single" boot option, had to delete recreate the users accounts.(use option do NOT delete user directories)
(posting from user account on effected machine, no issues since)
Reasonably sure it was a PAM or related update, but doing due diligence, and posting a super-mini how-to.