Security Bughunt

2017 - August - Amsterdam

2017 Target - IoT

Burak Kelebek - Securify, March 2017

Admin Custom Login WordPress plugin affected by persistent Cross-Site Scripting via Logo URL field


A persistent Cross-Site Scripting vulnerability has been encountered in the Admin Custom Login WordPress 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. The "logo_url" field does not validate <script> tags and does not perform output encoding.


For feedback or questions about this advisory mail us at sumofpwn at

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.



Tested versions

This issue was succesfully tested on the Admin Custom Login WordPress plugin version


There is currently no fix available.


Admin custom login plugin give ability to customize your WordPress admin login page according to you.

Pugin allows to change background color, background image, background slide show, login form color, login form font size, login form position, add social media icon on form and many more features.


As an admin, it's possible to upload a logo on the login page. The "logo_url" field does not validate <script> tags and does not perform output encoding.

Proof of concept

      <form action="http://<target>/wp-admin/options-general.php?page=admin_custom_login" method="POST">
         <input type="hidden" name="Action" value="logoSave"/>
         <input type="hidden" name="logo_image" value="http://<target>/wp-content/uploads/2016/06/scriptalert1script.jpeg"/>
         <input type="hidden" name="logo_width" value="200"/>
         <input type="hidden" name="logo_height" value="60"/>
         <input type="hidden" name="logo_url" value="&quot;><script>alert(1)</script>"/>
         <input type="hidden" name="logo_url_title" value="\\\\"/>
         <input type="submit"/>

After this request is executed, re-open the admin panel of WordPress and visit the Admin Custom Login page.