Aaron Patterson reports:
The attr_protected method allows developers to specify a blacklist of model attributes which users should not be allowed to assign to. By using a specially crafted request, attackers could circumvent this protection and alter values that were meant to be protected. All users running an affected release should either upgrade or use one of the work arounds immediately. Users should also consider switching from attr_protected to the whitelist method attr_accessible which is not vulnerable to this attack.