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Threat Intelligence: WordPress Zero-day

A zero-day vulnerability has been discovered affecting WP GDPR Compliance. WP GDPR Compliance is a WordPress plugin that aids website owners become GDPR compliant. The plugin is one of the more popular GDRP plugins available with over 100,000 active installations.

First seen roughly three weeks ago, the vulnerability used to gain access to WordPress sites and install backdoors. The plugin was removed earlier last week, however it was reinstated on November 7th after the release of version 1.4.3, which contained a patch for the vulnerability.

Attackers are actively exploiting the vulnerability for anyone running version 1.4.2 and older. According to researchers, “attackers are targeting a WP GDPR Compliance bug that allows them to make a call to one of the plugin’s internal functions and change settings for both the plugin, but also for the entire WordPress CMS.” At the time of writing this article, there are two techniques using the vulnerability.

In the first, the attacker uses the vulnerability to open the website’s registration system and will reset the default role for new accounts to administrator. The attacker will then create a new account that has usually been seen as “t2trollherten” and set back default user role for new accounts to subscriber. Public registration is then disabled and the attacker logs into their new account to install a backdoor on the site titled “wp-cache.php.” The backdoor contains a file manager, PHP eval() runner, and a terminal emulator.

The second technique is quieter and involves using the GDPR compliance vulnerability. It’s used to add a new task to WP-Cron, which is the built-in task scheduler. The attacker will download and install the plugin, which is later used to upload another backdoor on the site. This backdoor is also named wp-cahe.php, but is different than the previous one. Even though the second scenario is supposed to be quieter, it actually caused the zero-day to be discovered. This is because on some sites, the attacker’s exploitation routine failed to delete the plugin and site owners saw that a new plugin appeared.

Binary Defense Recommendation: For any users that believe to have been affected, users are advised to update to version 1.4.3. If a user runs an older version of the software, they are more susceptible to being attacked.  WordPress automatically has plugin updates set to manual, which can cause havoc for a user who does not remember to update. It is possible to change the plugin update setting’s, but that could cause compatibility issues if the plugin does not work with the current system and updates automatically.