The permissions on the /Users folder were also changed to be
world-writable, so that anyone could read and write to the
After considerable investigation by the folks in the ##osx-server
IRC room, it looks like the issue has been tied to two causes:
iTunes 11.2 being installed
iCloud’s Find My Mac being enabled.
That’s a pretty bad permissions bug. Trouton has a script that fixes all the damage (restore visibility to /Users and /Users/Shared, then run Repair Permissions), but note that you must turn off Find My Mac, or it will just happen all over again when you restart.