Bug 831573 (CVE-2012-2695)

Originally, the CVE-2012-2661 identifier has been assigned to the following issue:

A security flaw was found in the way rubygem-activerecord, the ActiveRecord pattern for ORM, performed SQL query generation based on the content of params hash, when nested query paramaters were provided. If a Ruby on Rails application directly passed request params to the 'where' method of an ActiveRecord class, a remote attacker could use this flaw to cause the 'params[:id]' to return a specially-crafted hash, resulting into the WHERE clause of the SQL statement to query an arbitrary table with value of attacker's choice, leading to disclosure of sensitive information. (bug 827363)

Recently (2012-06-12) it has been reported:
[1] https://groups.google.com/group/rubyonrails-security/browse_thread/thread/9782f44c4540cf59

that there still exists a variant of this attack, which is possible to exploit even when the upstream patch for the original CVE-2012-2661 issue has been applied. More from [1]:

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Due to the way Active Record handles nested query parameters, an attacker can use a specially crafted request to inject some forms of SQL into your application's SQL queries.

All users running an affected release should upgrade immediately. Please note, this vulnerability is a variant of CVE-2012-2661, even if you upgraded to address that issue, you must take action again.

Impacted code directly passes request params to the `where` method of an ActiveRecord class like this:

    Post.where(:id => params[:id]).all

An attacker can make a request that causes `params[:id]` to return a specially crafted hash that will cause the WHERE clause of the SQL statement to query an arbitrary table with some value. 

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Proposed upstream patches (see attachments).