Loofah is a general library for manipulating and transforming HTML/XML
documents and fragments. It's built on top of Nokogiri and libxml2, so
it's fast and has a nice API. Loofah excels at HTML sanitization (XSS
prevention). It includes some nice HTML sanitizers, which are based on
HTML5lib's whitelist, so it most likely won't make your codes less
secure.

Homepage:
https://github.com/flavorjones/loofah
