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 a remote code execution (RCE) vulnerability in the plugin Kanzu Support Desk.

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.

Details

The plugin’s file /includes/admin/class-ksd-admin.php is included when is_admin() is true:

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if ( is_admin() ) {
	require_once( KSD_PLUGIN_DIR .  'includes/admin/class-ksd-admin.php' );
}

That can be true without even being logged in to WordPress.

That file creates an instance of the KSD_Admin class, which is also defined in the same file:

return new KSD_Admin();

That class will run the function do_post_and_get_actions() during init:

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add_action( 'init', array( $this, 'do_post_and_get_actions' ) );

That function passes GET or POST input to the function do_action(), which leads to remote code execution:

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public function do_post_and_get_actions() {
	if ( isset( $_POST['ksd_action'] ) ) {
		do_action( $_POST['ksd_action'], $_POST );
	}
	if ( isset( $_GET['ksd_action'] ) ) {
		do_action( $_GET['ksd_action'], $_GET );
	}
}

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:

Proof of Concept

The following proof of concept will cause the WordPress action/function do_feed_rss to run.

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

http://[path to WordPress]/wp-admin/admin-post.php?ksd_action=do_feed_rss

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.

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