Pierluigi Paganini February 20, 2020

A new flaw was discovered in a WordPress plugin, this time experts found a zero-day vulnerability in the ThemeREX Addons to create admin accounts.

Security experts from WordFence have discovered a zero-day vulnerability in the ThemeREX Addons that was actively exploited by hackers in the wild to create user accounts with admin permissions.

According to WordFence, the ThemeREX Addons zero-day is currently installed on at least 44,000 websites.

This plugin was developed by the company ThemeRex to allow its customers to configure and installs one of over 460 commercial WordPress themes and templates that are available for sale in their online shop.

The vulnerability resides in a WordPress REST-API endpoint registered by the plugin which allows any PHP function to be executed without administrative permissions.

“One of the plugin’s functions registers a WordPress REST-API endpoint. When doing so, it does not verify that a request is coming from an administrative user. While this is not cause for concern on its own, the endpoint allows any PHP function to be executed, rather than being limited to a select few functions.” read the analysis published by WordFence. “The most worrisome capability that we are seeing actively attacked is the ability to create a new administrative user, which can be used for complete site takeover.”

A remote attacker could exploit the flaw to execute arbitrary code on WordPress installs running the flawed plugin, including code that can inject administrative user accounts.

Unfortunately, a patch has yet to be released, for this reason, experts suggest removing the ThemeREX Addons plugin if case sites are running version 1.6.50 and later.

“At the time of writing, this vulnerability is being actively exploited, therefore we urge users to temporarily remove the ThemeREX Addons plugin if you are running a version greater than 1.6.50 until a patch has been released.” continues the post.

The experts did not publish technical details of the zero-day because ongoing attacks are already exploiting it in the wild.

“We have intentionally provided minimal details in this post in an attempt to keep exploitation to a bare minimum while also informing WordPress site owners of this active campaign,” conclude the post.

“For the time being, we urge that site owners running the ThemeREX Addons plugin remove it from their sites immediately.”

Recently the issues with other WordPress plugins made the headlines:

• Jan. 2020 – An authentication bypass vulnerability in the InfiniteWP plugin that could potentially impact by more than 300,000 sites.
• Jan. 2020 – Over 200K WordPress sites are exposed to attacks due to a high severity cross-site request forgery (CSRF) bug in Code Snippets plugin.
• Feb. 2020 – A serious flaw in the ThemeGrill Demo Importer WordPress theme plugin with over 200,000 active installs can be exploited to wipe sites and gain admin access to the site.
• Feb. 2020 – A stored cross-site vulnerability in the GDPR Cookie Consent plugin that could potentially impact 700K users.

Pierluigi Paganini

(SecurityAffairs – hacking, IOTA foundation)

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