WordPress Core 6.2.1 Security & Maintenance Release – What You Need to Know

On May 16, 2023, the WordPress core team released WordPress 6.2.1, which contains patches for 5 vulnerabilities, including a Medium Severity Directory Traversal vulnerability, a Medium-Severity Cross-Site Scripting vulnerability, and several lower-severity vulnerabilities.

These patches have been backported to every version of WordPress since 4.1. WordPress has supported automatic core updates for security releases since WordPress 3.7, and the vast majority of WordPress sites should receive a patch for their major version of WordPress automatically over the next 24 hours. We recommend verifying that your site has been automatically updated to one of the patched versions. Patched versions are available for every major version of WordPress since 4.1, so you can update without risking compatibility issues.

If your site has not been updated automatically we strongly recommend updating manually as soon as possible, as one of the vulnerabilities patched in this release can be used by an attacker with a low-privileged contributor-level account to take over a site.

Vulnerability Analysis

As with every WordPress core release containing security fixes, the Wordfence Threat Intelligence team analyzed the code changes in detail to evaluate the impact of these vulnerabilities on our customers, and to ensure our customers remain protected.

WordPress Core is vulnerable to Directory Traversal in versions up to, and including, 6.2, via the ‘wp_lang’ parameter. This allows unauthenticated attackers to access and load arbitrary translation files. In cases where an attacker is able to upload a crafted translation file onto the site, such as via an upload form, this could be also used to perform a Cross-Site Scripting attack. This vulnerability would not be easy to exploit in an impactful manner on most configurations.

WordPress Core is vulnerable to Cross-Site Request Forgery due to missing nonce validation on the ‘wp_ajax_set_attachment_thumbnail’ AJAX function in versions up to, and including, 6.2. This allows unauthenticated users to update the thumbnail image associated with existing attachments, granted they can trick an authenticated user with appropriate permissions into performing an action, such as clicking a link. The impact of this vulnerability is incredibly minimal and we do not expect to see any exploitation of this weakness.

WordPress Core is vulnerable to stored Cross-Site Scripting in versions up to, and including, 6.2, due to insufficient validation of the protocol in the response when processing oEmbed discovery. This makes it possible for authenticated attackers with contributor-level and above permissions to use a crafted oEmbed payload at a remote URL to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

WordPress Core fails to sufficiently sanitize block attributes in versions up to, and including, 6.2. This makes it possible for authenticated attackers with contributor-level and above permissions to embed arbitrary content in HTML comments on the page, though Cross-Site scripting may be possible when combined with an additional vulnerability. Please note that this would only affect sites utilizing a block editor compatible theme.

WordPress Core processes shortcodes in user-generated content on block themes in versions up to, and including, 6.2. This could allow unauthenticated attackers to execute shortcodes via submitting comments or other content, allowing them to exploit vulnerabilities that typically require Subscriber or Contributor-level permissions. While this is likely to have minimal impact on its own, it can significantly increase the severity and exploitability of other vulnerabilities.

Conclusion

In today’s article, we covered five vulnerabilities patched in the WordPress 6.2.1 Security and Maintenance Release. Most actively used WordPress sites should be patched via automatic updates within the next 24 hours.

The Wordfence firewall’s built-in directory traversal protection should block attempts to exploit the directory traversal vulnerability, and it would typically only be impactful when exploited by a skilled attacker in certain configurations. Most of the other issues fixed today are similar in that they require specific configurations or circumstances, such as other vulnerable plugins, to impactfully exploit.

However, we urge all site owners to verify that WordPress is updated as soon as possible since it is not practical to deploy a firewall rule that protects against the oEmbed issue and as such any site with untrusted contributor-level users may be at risk.

As always, we strongly recommend updating your site to a patched version of WordPress if it hasn’t been updated automatically. As long as you are running a version of WordPress greater than 4.1, an update is available to patch these vulnerabilities while keeping you on the same major version, so you will not need to worry about compatibility issues.

Special thanks to Wordfence QA Lead Matt Rusnak for finding the directory traversal vulnerability that we responsibly disclosed, and to John Blackbourn of the WordPress security team, Jakub Żoczek of Securitum, and Liam Gladdy of WP Engine for responsibly disclosing these issues.
This article was written by Ramuel Gall, a former Wordfence Senior Security Researcher.