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COMPASS SECURITY ADVISORY http://www.csnc.ch/

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CVE ID : CVE-2009-4505

Product: OpenCMS OAMP Comments Module

Vendor: Open Source, Alkacon GmbH (Cologne, Germany)

Subject: Cross-site scripting (XSS)

Risk: High

Effect: Anonymously exploitable

Author: Cyrill Brunschwiler ([email protected])

Date: March 24th 2010

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Introduction:

Cyrill Brunschwiler of Compass Security discovered a web application
security flaw in the OpenCMS OAMP comments module.

Description:

The OAMP comments module allows OpenCMS users to add comments to pages.
However, the comment module reflects unfiltered user input. Following
that, attackers could injected HTML code and JavaScript code which gets
executed within all visitors web browsers.

Exploiting the vulnerability will lead to so-called cross-site scripting
(XSS) and allows the impersonation of logged-in OpenCMS web and
workplace
users. Attackers could also embbed arbitrary content such as faked login
forms or redirect OpenCMS users to malware pages.

Vulnerable:

OAMP comments module version 1.0.0

Patches:

Get the latest version at http://cvs.opencms.org/

Fix:

All output must be encoded using HTML entities. For that purpose the
escapeXml attribute must not being set false on all c:out tags.
Moreover,
all fmt:param outputs must be encoded as well.

Example:
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions&quot; %>
<fmt:param value="${fn:escapeXml(comment.field['name'])}" />

Alternatively one could use the OWASP ESAPI (Enterprise Security API) to
encode all output. For more details on the OWASP ESAPI consult the
google
code repository and see http://www.owasp.org/index.php/ESAPI

Example:
String clean = ESAPI.encoder().encodeForHTML(maliciousInput);

Milestones:

December 24th 2009, Vulnerability discovered
January 6th 2010, Vendor notified
March 13rd 2010, Fixed in CVS (m.jaeger)

References:

OpenCMS - http://www.opencms.org/en/

OpenCms from Alkacon Software is a professional, easy to use website
content management system. OpenCms helps content managers worldwide to
create and maintain beautiful websites fast and efficiently.

OpenCMS OAMP Modules -
http://www.alkacon.com/en/products/oamp/index.html

The Alkacon OpenCms Add-On Module Package (also called OAMP) is a set of
free, open source extension modules for OpenCms. Alkacon OAMP adds
front-
end related features to OpenCms that may be useful in case special
functionalities are required.

XSS - http://www.owasp.org/index.php/Cross-site_Scripting_&#40;XSS&#41;

Cross-Site Scripting attacks are a type of injection problem, in which
malicious scripts are injected into the otherwise benign and trusted web
sites. Cross-site scripting (XSS) attacks occur when an attacker uses a
web application to send malicious code, generally in the form of a
browser
side script, to a different end user. Flaws that allow these attacks to
succeed are quite widespread and occur anywhere a web application uses
input from a user in the output it generates without validating or
encoding it.

An attacker can use XSS to send a malicious script to an unsuspecting
user. The end user's browser has no way to know that the script should
not
be trusted, and will execute the script. Because it thinks the script
came
from a trusted source, the malicious script can access any cookies,
session tokens, or other sensitive information retained by your browser
and used with that site. These scripts can even rewrite the content of
the
HTML page.