SQL injection vulnerability in activerecord/lib/active_record/connection_adapters/postgresql/cast.rb in Active Record in Ruby on Rails 4.0.x before 4.0.3, and 4.1.0.beta1, when PostgreSQL is used, allows remote attackers to execute "add data" SQL commands via vectors involving \ (backslash) characters that are not properly handled in operations on array columns.
https://groups.google.com/forum/message/raw?msg=rubyonrails-security/Wu96YkTUR6s/pPLBMZrlwvYJ