Hackers exploit WordPress plugin flaw that gives full control of millions of sites

Hackers are actively exploiting a critical vulnerability in a widely used WordPress plugin that gives them the ability to take complete control of millions of sites, researchers said.

The vulnerability, which carries a severity rating of 8.8 out of a possible 10, is present in Elementor Pro, a premium plugin running on more than 12 million sites powered by the WordPress content management system. Elementor Pro allows users to create high-quality websites using a wide range of tools, one of which is WooCommerce, a separate WordPress plugin. When those conditions are met, anyone with an account on the site—say a subscriber or customer—can create new accounts that have full administrator privileges.

The vulnerability was discovered by Jerome Bruandet, a researcher with security firm NinTechNet. Last week, Elementor, the developer of the Elementor Pro plugin, released version 3.11.7, which patched the flaw. In a post published on Tuesday, Bruandet wrote:

An authenticated attacker can leverage the vulnerability to create an administrator account by enabling registration (users_can_register) and setting the default role (default_role) to “administrator”, change the administrator email address (admin_email) or, as shown below, redirect all traffic to an external malicious website by changing siteurl among many other possibilities:
MariaDB [example]> SELECT * FROM `wp_options` WHERE `option_name`='siteurl';
+-----------+-------------+------------------+----------+
| option_id | option_name | option_value     | autoload |
+-----------+-------------+------------------+----------+
|		 1 | siteurl     | https://evil.com | yes 	 |
+-----------+-------------+------------------+----------+
1 row in set (0.001 sec)

Now, researchers with a separate security firm, PatchStack, report that the vulnerability is under active exploitation. Attacks are coming from a variety of IP addresses, including:

193.169.194.63
193.169.195.64
194.135.30.6

Files uploaded to compromised sites often have the following names:

wp-resortpack.zip
wp-rate.php
lll.zip

URLs of compromised sites are often being changed to:

away[dot]trackersline[dot]com

The broken access control vulnerability stems from Elementor Pro’s use of the “elementor-pro/modules/woocommerce/module.php” component. When WooCommerce is running, this script registers the following AJAX actions:

/**
 * Register Ajax Actions.
 *
 * Registers ajax action used by the Editor js.
 *
 * @since 3.5.0
 *
 * @param Ajax $ajax
 */
public function register_ajax_actions( Ajax $ajax ) {
   // `woocommerce_update_page_option` is called in the editor save-show-modal.js.
   $ajax->register_ajax_action( 'pro_woocommerce_update_page_option', [ $this, 'update_page_option' ] );
   $ajax->register_ajax_action( 'pro_woocommerce_mock_notices', [ $this, 'woocommerce_mock_notices' ] );
}

and

/**
 * Update Page Option.
 *
 * Ajax action can be used to update any WooCommerce option.
 *
 * @since 3.5.0
 *
 * @param array $data
 */
public function update_page_option( $data ) {
   update_option( $data['option_name'], $data['editor_post_id'] );
}

The update_option function “is supposed to allow the Administrator or the Shop Manager to update some specific WooCommerce options, but user input aren’t validated and the function lacks a capability check to restrict its access to a high privileged user only,” Bruandet explained. He continued:

Elementor uses its own AJAX handler to manage most of its AJAX actions, including pro_woocommerce_update_page_option, with the global elementor_ajax action. It is located in the “elementor/core/common/modules/ajax/module.php” script of the free version (which is required to run Elementor Pro) :
/**
 * Handle ajax request.
 *
 * Verify ajax nonce, and run all the registered actions for this request.
 *
 * Fired by `wp_ajax_elementor_ajax` action.
 *
 * @since 2.0.0
 * @access public
 */
public function handle_ajax_request() {
   if ( ! $this->verify_request_nonce() ) {
  	$this->add_response_data( false, esc_html__( 'Token Expired.', 'elementor' ) )
     	->send_error( Exceptions::UNAUTHORIZED );
   }
   ...

Anyone using Elementor Pro should ensure they’re running 3.11.7 or later, as all previous versions are vulnerable. It’s also a good idea for these users to check their sites for the signs of infection listed in the PatchStack post.