source: http://www.securityfocus.com/bid/14960/info

A remote command execution vulnerability affects the application.

The revision control function of the TWikiUsers script uses the backtick shell metacharacter to construct a command line. An attacker may use a specially crafted URI to execute arbitrary commands through the shell.

This attack would occur in the context of the vulnerable application and can facilitate unauthorized remote access. 

%INCLUDE{ "Main.TWikiUsers" rev="2|less /etc/passwd" }% 