If a URL is from an untrusted source, commands can be injected into it for remote code execution with the ; character. image = MiniMagick::Image.open(remoteurl) image.resize "5x5" image.format "gif" image.write "localcopy.gif" ./hcatlin-mini_magick-1.3.1/lib/mini_magick.rb Lines 172 command = "#{MiniMagick.processor} #{command} {args.join(' ')}".strip 173 174 if ::MiniMagick.use_subexec 175 sub = Subexec.run(command, :timeout => MiniMagick.timeout) 176 exit_status = sub.exitstatus 177 output = sub.output 178 else 179 output = `{command} 2>&1` 180 exit_status = $?.exitstatus 181 end The .strip will only remove whitespace from the beginning and end of the command.