Security Experts:

Critical Flaw in SEO Plugin Exposed Many WordPress Sites to Attacks

A critical vulnerability in the Rank Math SEO plugin for WordPress could allow attackers to lock administrators out of their own websites, WordPress security company Defiant reports.

Meant to help site owners get access to search engine optimization (SEO) tools that would improve their SEO and attract more traffic, the plugin has over 200,000 installations.

Featuring a CVSS score of 10, the vulnerability impacts the plugin’s ability to update metadata on posts. For this feature, the plugin registered a REST-API endpoint, rankmath/v1/updateMeta, but the lack of a permission_callback for capability checking exposes it to attacks.

The endpoint uses the update_metadata function to delete or update metadata for posts, comments, and terms, but can also update metadata for users, which results in this critical vulnerability.

The user permissions in WordPress are stored in the usermeta table, and the flaw could result in an unauthenticated attacker granting any registered user administrative privileges.

What’s more, the attacker could completely revoke an existing administrator’s privileges, which would essentially mean locking the admin out of their own website.

“Note that these attacks are only the most critical possibilities. Depending on the other plugins installed on a site, the ability to update post, term, and comment metadata could potentially be used for many other exploits such as Cross-Site Scripting (XSS),” Defiant explains.

Another vulnerability the security firm discovered in Rank Math could result in the creation of redirects via an unprotected REST API endpoint.

The issue resides in the failure to include a permission_callback for capability checking in the registered REST-API endpoint rankmath/v1/updateRedirection.

A function called by the endpoint could be used to create new redirects or modify existing redirects. It did not allow redirects to existing files or folders on the server, including the site’s main page, thus limiting the damage an unauthenticated attacker could cause.

“While an attacker could create a redirect from most locations on the site, including new locations, or any existing post or page other than the homepage, they could not redirect visitors immediately upon accessing the site,” Defiant notes.

The vulnerabilities were discovered on March 23 and a patch was released on March 26. Site admins are advised to update to the patched version of Rank Math as soon as possible.

“These vulnerabilities have been fully patched in version 10.0.41, and we strongly recommend that all users of this plugin upgrade to the latest version available immediately,” Defiant concludes.

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