In \apps\phpsysinfo3.1.12/language/language.php
60: echo file_get_contents(APP_ROOT . '/language/' . $lang . '.xml');
is presented where $lang is defined as:
52: $lang = basename($_GET['lang']);
Which can be exploited like
localhost/phpsysinfo/language/language.php?lang=../../../stufftoinclude
which can be extended with nullbytes to contain any other file that isn't
XML too.
