XSS vulnerability in the white list sanitizer in the rails-html-sanitizer gem was reported. Carefully crafted strings can cause user input to bypass the sanitization in the white list sanitizer which will can lead to an XSS attack.

External References:

https://groups.google.com/forum/#!msg/rubyonrails-security/uh--W4TDwmI/m_CVZtdbFQAJ
http://weblog.rubyonrails.org/2016/1/25/Rails-5-0-0-beta1-1-4-2-5-1-4-1-14-1-3-2-22-1-and-rails-html-sanitizer-1-0-3-have-been-released/