Cross-site scripting (XSS) vulnerability in json/encoding.rb in Active Support in Ruby on Rails 3.x and 4.1.x before 4.1.11 and 4.2.x before 4.2.2 allows remote attackers to inject arbitrary web script or HTML via a crafted Hash that is mishandled during JSON encoding.
https://groups.google.com/forum/message/raw?msg=rubyonrails-security/7VlB_pck3hU/3QZrGIaQW6cJ
http://www.securitytracker.com/id/1033755
http://www.securityfocus.com/bid/75231