Vendor  : phpBB Group
URL     : http://www.phpbb.com
Version : phpBB 2.0.6d && Earlier
Risk    : Cross Site Scripting



Description:
phpBB is a high powered, fully scalable, and highly customisable open-source 
bulletin board package. phpBB has a user-friendly interface, simple and straight 
forward administration panel, and helpful FAQ. Based on the powerful PHP server 
language and your choice of MySQL, MS-SQL, PostgreSQL or Access/ODBC database 
servers, phpBB is the ideal free community solution for all web sites.



Problem:
phpBB is a great forum system used by many millions of people. It is one of 
the more secure of the forum systems, but has a few issues still present; both 
of which allow for XSS (Cross Site Scripting). This problem presents itself in 
two different places.One of these places is viewtopic.php and the other is 
viewforum.php Below are examples along with a brief explanation on how to 
replicate this issue.

viewforum.php?f=[FNUM]&topicdays=[DNUM][XSS]

FNUM is a valid forum number. DNUM is the number of days to check. If you get no 
results with the number 1 for example try  the number 99 and so forth and so on. 
XSS is whatever code is injected.

viewtopic.php?t=[TNUM]&postdays=[DNUM][XSS]

This is nearly the same issue as above, it just happens to be present in multiple 
files. The only difference is TNUM is a valid topic id number. Remember, the query 
must display results in order for the XSS to take place. Additionally the offset 
(start) variable may be used to get results, but in most cases is unnecessary. 
Examples are below though.



Examples:
viewforum.php?f=1&topicdays=99"><script>alert(document.cookie)</script>&start=30
viewtopic.php?t=10&postdays=99"><script>alert(document.cookie)</script>&start=20



Solution:
I have released a fix for this vulnerability. It requires a valid integer for the
affected variables, and thus eliminates this vulnerability from taking place. You
can find the fix by following the link below.

http://www.gulftech.org/vuln/phpBB2.0.6dfix.rar

Alternatively you can do it yourself by following the instructions listed below.


-----[ OPEN ]-----------------------------------

viewforum.php

-----[ FIND ]-----------------------------------

if ( !empty($HTTP_POST_VARS['topicdays']) || !empty($HTTP_GET_VARS['topicdays']) )
{
	$topic_days = ( !empty($HTTP_POST_VARS['topicdays']) ) ? $HTTP_POST_VARS['topicdays'] : $HTTP_GET_VARS['topicdays'];
	$min_topic_time = time() - ($topic_days * 86400);

-----[ REPLACE WITH ]---------------------------

if ( !empty($HTTP_POST_VARS['topicdays']) || !empty($HTTP_GET_VARS['topicdays']) )
{

///////////////////////////////////////////////////////////////////
// Lets Do Away With These Problems By Requiring A Valid Integer //
// Fix By JeiAr // http://www.gulftech.org // Friday 03 12, 2004 //
///////////////////////////////////////////////////////////////////
	
	$topic_days = ( !empty($HTTP_POST_VARS['topicdays']) ) ? intval($HTTP_POST_VARS['topicdays']) : intval($HTTP_GET_VARS['topicdays']);
	$min_topic_time = time() - ($topic_days * 86400);





-----[ OPEN ]-----------------------------------

viewtopic.php

-----[ FIND ]-----------------------------------

if( !empty($HTTP_POST_VARS['postdays']) || !empty($HTTP_GET_VARS['postdays']) )
{
	$post_days = ( !empty($HTTP_POST_VARS['postdays']) ) ? $HTTP_POST_VARS['postdays'] : $HTTP_GET_VARS['postdays'];
	$min_post_time = time() - (intval($post_days) * 86400);

-----[ REPLACE WITH ]---------------------------

if( !empty($HTTP_POST_VARS['postdays']) || !empty($HTTP_GET_VARS['postdays']) )
{

///////////////////////////////////////////////////////////////////
// Lets Do Away With These Problems By Requiring A Valid Integer //
// Fix By JeiAr // http://www.gulftech.org // Friday 03 12, 2004 //
///////////////////////////////////////////////////////////////////
	
	$post_days = ( !empty($HTTP_POST_VARS['postdays']) ) ? intval($HTTP_POST_VARS['postdays']) : intval($HTTP_GET_VARS['postdays']);
	$min_post_time = time() - (intval($post_days) * 86400);





phpBB development team will be releasing an official fix soon. Please check their 
website, or the SourceForge projects page of phpBB for any updates. The SourceForge 
projects page for phpBB can be located @ http://sourceforge.net/projects/phpbb The 
fix supplied here should suffice though. If you feel this is incorrect please contact 
me with details of any problems you experience. And a big thanks to Meik Sievertsen 
and the rest of the phpBB team for addressing these issues in a very prompt and 
professional manner. Original advisory located @ http://www.gulftech.org/03122004.php



Credits:
Credits go to JeiAr of the GulfTech Security Research Team. 
http://www.gulftech.org