Advisory: Stored XSS Vulnerability in CMS Serendipity v.2.0-rc1
Advisory ID: SROEADV-2014-02
Author: Steffen Rцsemann
Affected Software: CMS Serendipity v.2.0-rc1 (Release: 20th Dec 2014)
Vendor URL: http://www.s9y.org/
Vendor Status: fixed
CVE-ID: -

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Vulnerability Description:

The Content Management System Serendipity v.2.0-rc1 has a stored XSS-vulnerability in its comment functionality. Arbitrary HTML- and/or JavaScriptcode is stored in the database. On the frontend side, it gets sanitized, while on the administrative backend, where new comments are displayed to the administrator after login, it gets immidiately executed.

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Technical Details:

If an attacker is posting arbitrary HTML- and/or JavaScriptcode in a comment, which for example is located in the following URL, it will be stored in the database without being sanitized.

http://{HOSTNAME/DOMAIN}/serendipity/index.php?/archives/{TITLE-OF-THE-BLOG-ENTRY}.html#comments

When the comments are displayed on the frontend, they will be sanitized, while on the administrative backend it gets displayed unsanitized and is being executed, because the latest comments are shown, after an administrative user has been logged in to the following URL:

http://{HOSTNAME/DOMAIN}/serendipity/serendipity_admin.php

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Solution:

Update to the latest version

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Disclosure Timeline:

22-Dec-2014 – found the vulnerability
23-Dec-2014 - informed the developers
23-Dec-2014 - release date of this security advisory
23-Dec-2014 - response and fix by vendor
23-Dec-2014 - post on FullDisclosure

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Credits:

Vulnerability found and advisory written by Steffen Rцsemann.

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References:

http://blog.s9y.org/archives/259-Serendipity-2.0-rc2-released.html
http://sroesemann.blogspot.de