Permissions of /Users keep changing back to drwxrwxrwx
This problem was caused by a bug introduced by an Apple software update. iTunes 11.2.1 has been released to fix the issue.


  iTunes 11.2.1
  
  Impact: A local user can compromise other local user accounts
  
  Description: Upon each reboot, the permissions for the /Users and /Users/Shared directories would be set to world-writable, allowing modification of these directories. This issue was addressed with improved permission handling.


This vulnerability was assigned the security identifier CVE-2014-1347.