Aaron Patterson (tenderlove) reports:

Circumvention of attr_protected

There is a vulnerability in the attr_protected method in ActiveRecord. This 
vulnerability has been assigned the CVE identifier CVE-2013-0276.

Versions Affected:  All.
Not affected:       Applications using attr_accessible
Fixed Versions:     3.2.12, 3.1.11

Impact 
------
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.

Releases 
-------- 
The FIXED releases are available at the normal locations. 

Workarounds 
----------- 
The only feasible work around for this issue is to convert the application to 
use attr_accessible instead of attr_protected.

Patches 
------- 
To aid users who aren't able to upgrade immediately we have provided patches 
for the two supported release series.  They are in git-am format and consist 
of a single changeset. 

* 3-2-attr_protected.patch - Patch for 3.2 series 
* 3-1-attr_protected.patch - Patch for 3.1 series 
* 3-0-attr_protected.patch - Patch for 3.0 series
* 2-3-attr_protected.patch - Patch for 2.3 series

Please note that only the 3.1.x and 3.2.x series are supported at present.  
Users of earlier unsupported releases are advised to upgrade as soon as 
possible as we cannot guarantee the continued availability of security fixes 
for unsupported releases.

Credits 
-------
Thanks to joernchen of Phenoelit and Ryan Koppenhaver of Matasano Security for 
reporting the vulnerability to us and working closely with us on a fix.