lib/entry_controller.rb in the fastreader Gem 1.0.8 for Ruby allows remote attackers to execute arbitrary commands via shell metacharacters in a URL.
http://www.openwall.com/lists/oss-security/2013/03/19/9
http://packetstormsecurity.com/files/120845/Ruby-Gem-Fastreader-1.0.8-Code-Execution.html
http://packetstormsecurity.com/files/120776/Ruby-Gem-Fastreader-1.0.8-Command-Execution.html