Bypass XSS filter in PHPNUKE x <= 7.9 ( Research Advisory )

Advisory Text :

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[Bypass XSS filter in PHPNUKE 7.9=>x cXIb8O3.21]

Author: Maksymilian Arciemowicz ( cXIb8O3 )
Date: 14.12.2005
from SECURITYREASON.COM

- --- 0.Description ---
PHP-Nuke is a Web Portal System, storytelling software, news system, online
community or whatever you want to call it. Its goal is to have an automated
web site to distribute news and articles with user system. Each user can
submit comments to discuss the articles, similar to Slashdot and many
others. Features: web admin, polls/surveys with comment, statistics, user
customizable box, themes manager, friendly admin GUI, moderation system,
sections manager, banner system, backend/headlines generation, Yahoo like
search engine, Ephemerids manager, file manager, download manager, faq
manager, advanced blocks system, reviews system, newsletter, content
management, encyclopedia generator, md5 password encryption, phpBB Forums
integration, support for 25 languages, 100% modular and more. Written 100%
in PHP and requires Apache, PHP and a SQL Database Server. Supports MySQL,
PostgreSQL, Adabas, mSQL and many others.

- --- 1. Bypass XSS filter ---

In PHPnuke is (file includes/mainfile.php).

- -168-193---
if (!defined('ADMIN_FILE') && !file_exists('includes/nukesentinel.php')) {
foreach ($_GET as $sec_key => $secvalue) {
if ((eregi("<[^>]*script*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*object*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*iframe*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*applet*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*meta*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*style*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*form*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*img*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*onmouseover*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*body*\"?[^>]*>", $secvalue)) ||
(eregi("$[^>]*\"?[^)]*$", $secvalue)) ||
(eregi("\"", $secvalue)) ||
(eregi("forum_admin", $sec_key)) ||
(eregi("inside_mod", $sec_key))) {
die ($htmltags);
}
}

foreach ($_POST as $secvalue) {
if ((eregi("<[^>]*onmouseover*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]script*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*body*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]style*\"?[^>]*>", $secvalue))) {
die ($htmltags);
}
}
}
- -168-193---

This functions deletes from input html tags like:

- <script>
- <object>
- <iframe>
- <applet>
- <meta>
- <style>
- <form>
- <img>
- <onmouseover>
- <body>

etc.

Ok. But if we sent to script:

# <iframe src=http://securityreason? < Hi

The function don't find wrong tags.
And broswer read this

"<iframe src=http://securityreason? < Hi"

and change "<" to ">".
Result:

# <iframe src=http://securityreason? > Hi

I have checked this in IE, Mozilla, Opera, Links, Lynx etc.
Only don't work in konqueror.

- --- 2. XSS ---

2.0 http://[HOST]/[DIR]/modules.php?name=Search

Insert:

<iframe src=http://securityreason.com?phpnuke79 <

And have you xss.

2.1 http://[HOST]/[DIR]/modules.php?name=Web_Links

Insert:

<iframe src=http://securityreason.com?phpnuke79 <

and more.

- --- 3. How to fix ---

Change xss filter in mainfile.php

- ---
if (!defined('ADMIN_FILE')) {
foreach ($_GET as $sec_key => $secvalue) {
if ((eregi("<[^>]*script*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*object*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*iframe*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*applet*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*meta*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*style*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*form*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*img*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]*onmouseover*\"?[^>]*>", $secvalue)) ||
(eregi("$[^>]*\"?[^)]*$", $secvalue)) ||
(eregi("\"", $secvalue)) ||
(eregi("forum_admin", $sec_key)) ||
(eregi("inside_mod", $sec_key))) {
die ("<center><img src=images/logo.gif><br><br><b>The html tags you
attempted to use are not allowed</b><br><br>[ <a
href=\"javascript:history.go(-1)\"><b>Go Back</b></a> ]");
}
}

foreach ($_POST as $secvalue) {
if ((eregi("<[^>]*onmouseover*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]script*\"?[^>]*>", $secvalue)) ||
(eregi("<[^>]style*\"?[^>]*>", $secvalue))) {
die ("<center><img src=images/logo.gif><br><br><b>The html tags you
attempted to use are not allowed</b><br><br>[ <a
href=\"javascript:history.go(-1)\"><b>Go Back</b></a> ]");
}
}
}
- ---

to

- ---
if (!defined('ADMIN_FILE')) {
foreach ($_GET as $sec_key => $secvalue) {
if((eregi("<[^>]*script*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*object*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*iframe*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*applet*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*meta*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*style*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*form*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*img*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*onmouseover *\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*body *\"?[^>]*", $secvalue)) ||
(eregi("$[^>]*\"?[^)]*$", $secvalue)) ||
(eregi("\"", $secvalue)) ||
(eregi("forum_admin", $sec_key)) ||
(eregi("inside_mod", $sec_key)))
{
die ($htmltags);
}

}

foreach ($_POST as $secvalue) {
if ((eregi("<[^>]*iframe*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*object*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*applet*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*meta*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*form*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*img*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*onmouseover*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]script*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]*body*\"?[^>]*", $secvalue)) ||
(eregi("<[^>]style*\"?[^>]*", $secvalue)))
{
die ($htmltags);
}
}
}
- ---

thx nukefixes.com

- --- 4. Greets ---

sp3x, nukefixes.com

- --- 5.Contact ---
Author: Maksymilian Arciemowicz < cXIb8O3 >
Email: max [at] jestsuper [dot] pl or cxib [at] securityreason [dot] com
GPG-KEY: http://securityreason.com/key/Arciemowicz.Maksymilian.gpg
SecurityReason.Com
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