Cross-site scripting (XSS) vulnerability in the simple_format helper in actionpack/lib/action_view/helpers/text_helper.rb in Ruby on Rails 4.x before 4.0.2 allows remote attackers to inject arbitrary web script or HTML via a crafted HTML attribute.
https://groups.google.com/forum/message/raw?msg=ruby-security-ann/5ZI1-H5OoIM/ZNq4FoR2GnIJ
http://www.securityfocus.com/bid/64071
http://weblog.rubyonrails.org/2013/12/3/Rails_3_2_16_and_4_0_2_have_been_released/