lib/mini_magick.rb in the MiniMagick Gem 1.3.1 for Ruby allows remote attackers to execute arbitrary commands via shell metacharacters in a URL.
http://www.securityfocus.com/bid/58448
http://www.openwall.com/lists/oss-security/2013/03/19/9
http://seclists.org/fulldisclosure/2013/Mar/123
http://packetstormsecurity.com/files/120777/Ruby-Gem-Minimagic-Command-Execution.html