Jurgen Kloosterman, July 2016

Cross-Site Scripting vulnerability in Caldera Forms WordPress Plugin


A Cross-Site Scripting vulnerability was found in the Caldera Forms 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. In order to exploit this issue, the attacker has to lure/force a logged on WordPress Administrator into opening a malicious website.


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.



Tested versions

This issue was successfully tested on Caldera Forms WordPress Plugin version


The Caldera Forms developers issued a fix in Caldera Forms 1.4.2 which adds nonces for multiple functions (including create_form()), therefore effectively solving this issue.


A Cross-Site Scripting vulnerability was found in the Caldera Forms WordPress Plugin, as the source code such as the creating new forms does not include an anti-Cross-Site Request Forgery token.


A Stored Cross-Site Scripting vulnerability exists in the Caldera Forms WordPress plugin. This vulnerability allows an attacker to perform any action with the privileges of the target user. The affected code is not protected with an anti-Cross-Site Request Forgery token. Consequently, it can be exploited by luring the target user into clicking a specially crafted link or visiting a malicious website (or advertisement).

The vulnerability exists in the file caldera-forms/classes/admin.php and is located in the function create_form().

1417: echo $newform['ID'];

The vulnerability can be exploited using a specially crafted HTTP POST request to obtain the CSRF token and execute Javascript. In order to exploit this issue the target user must have an active session in the Administrator control panel and visit a malicious site (or advertisement).

Proof of concept

<!DOCTYPE html>
      <form action="http://<target>/wp-admin/admin-ajax.php" method="POST">
            <input name="before" value="serialize_modal_form"/>
            <input name="data" value="name=%3Cscript%3Ealert(1)%3C%2Fscript%3E"/>
            <input name="template" value="0"/>
            <input name="callback" value="new_form_redirect"/>
            <input name="modalAutoclose" value="new_form"/>
            <input name="action" value="create_form"/>
            <button type="submit">send</button>