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Drupal Link to Us Module Contains XSS Vulnerability
From: "Justin C. Klein Keane" <Justin () MadIrish net>
Date: Wed, 17 Sep 2008 15:58:17 -0400

* Date: Sept 15, 2008
* Security risk: low
* Exploitable from: Remote
* Vulnerability: Cross site scripting


Drupal (http://www.drupal.org) is a robust content management system
(CMS) that provides extensibility through hundreds of third party
modules.  While the security of Drupal core modules is vetted by a
central security team, third party modules are not reviewed for security.

The Link to Us module (http://drupal.org/project/link_to_us), created by
Greg Holsclaw (http://www.tech-wanderings.com/drupal-link-to-us-module)
is designed to users to link directly to the content of a Drupal site by
copying and pasting HTML code onto their own site.  Unfortunately the
module does not properly sanitize input and exposes a cross site
scripting vulnerability.  Users with privileges to manage the Link to Us
module can insert malicious HTML or JavaScript that is rendered when a
user clicks the 'Share this page' link.

Vulnerable Versions

5.x-10 was tested and shown vulnerable.

Testing for Vulnerability

If a user with permissions to manage Link to Us goes to Administer->Site
Configuration->Link to Us and enters "<script>alert('foo');</script>"
into the "Link page header:" textarea the input is not sanitized,
presenting a JavaScript alert that reads 'foo' whenever anyone clicks
the 'Share this page' link at the bottom of content with the Link to Us
module (full details below).


Depending on configuration, this vulnerability allows users with
permissions to the Link to Us module to inject malicious content that
could be displayed to web site users.  Such content could include links
to malware that could lead to possible system compromise.

Determining Version

The link_to_us.info page for vulnerable versions displays the following

; $Id:
name = Link To Us Module
description = Add Link to this site functionality.

; Information added by drupal.org packaging script on 2008-03-13
version = "5.x-1.0"
project = "link_to_us"
datestamp = "1205451908"

Determining version information on Drupal sites is trivial in many cases
(ref http://www.madirish.net/?article=214).

Vendor Response

Vendor initially contacted on July 2, 2008.  Although a patch was
created, according to the Drupal security team's policy
(http://drupal.org/node/32750), they delay releases of patches or
details until a fixed timeframe.  Drupal security has said an
announcement and patch should be forthcoming and available this
Wednesday, September 17, 2008.

Mad Irish

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