Cross-site scripting (XSS) vulnerability in activesupport/lib/active_support/core_ext/string/output_safety.rb in Ruby on Rails 2.x before 2.3.13 3.0.x before 3.0.10 and 3.1.x before 3.1.0.rc5 allows remote attackers to inject arbitrary web script or HTML via a malformed Unicode string related to a \UTF-8 escaping vulnerability.\