source: http://www.securityfocus.com/bid/24161/info

Ruby on Rails is prone to a script-injection vulnerability because the application fails to properly sanitize user-supplied input before using it in dynamically generated content.

Attacker-supplied script code would run in the context of the affected site, potentially allowing the attacker to steal cookie-based authentication credentials and to control how the site is rendered to the user; other attacks are also possible.

This issue affects Ruby on Rails 1.2.3; other versions may also be affected. 

http://www.exploit-db.com/sploits/30089.tgz