A few weeks ago, our Threat Intelligence team discovered several vulnerabilities present in Page Builder: PageLayer – Drag and Drop website builder, a WordPress plugin actively installed on over 200,000 sites. The plugin is from the same creators as wpCentral, a plugin within which we recently discovered a privilege escalation vulnerability.

One flaw allowed any authenticated user with subscriber-level and above permissions the ability to update and modify posts with malicious content, amongst many other things. A second flaw allowed attackers to forge a request on behalf of a site’s administrator to modify the settings of the plugin which could allow for malicious Javascript injection.

We initially reached out to the plugin’s developer on April 30, 2020 and after establishing an appropriate communication channel, we provided the full disclosure on May 1, 2020. They responded quickly on May 2, 2020 letting us know that they were beginning to work on fixes. An initial patch was released on May 2, 2020 and an optimal patch was released on May 6, 2020.

These are considered high-level security issues that could potentially lead to attackers wiping your site’s content or taking over your site. We highly recommend an immediate update to the latest version available at the time of this publication, which is version 1.1.4.

Wordfence Premium customers received a new firewall rule on April 30, 2020, to protect against exploits targeting this vulnerability. Free Wordfence users will receive this rule after thirty days, on May 30, 2020.

PageLayer is a very easy to use WordPress page builder plugin that claims to work with nearly all themes on the market and in the WordPress repository. It provides extended customization of pages through the use of widgets that can add page elements like buttons, tables, excerpts, products and more.

We discovered that nearly all of the AJAX action endpoints in this plugin failed to include permission checks. This meant that these actions could be executed by anyone authenticated on the site, including subscriber-level users. As standard, these AJAX endpoints only checked to see if a request was coming from /wp-admin through an authenticated session and did not check the capabilities of the user sending the request.

There were nonce checks in use in all of these functions, but nonces can be easily compromised if incorrectly implemented – for example, if a usable nonce is displayed within the source code of the site’s output. Unfortunately for the PageLayer plugin, this is precisely what happened. A usable nonce was visible in the header section of the source code of any page that had previously been edited using the PageLayer plugin. Any site visitor could find this nonce, whether they were logged in or not, allowing any unauthenticated user the ability to obtain a legitimate nonce for the plugin’s AJAX actions.

Using a single nonce as the mechanism for authorization control caused various security issues in the functionalities of the page builder due to this nonce being so easily obtainable.

WordPress nonces should never be used as a means of authorization as they can easily be compromised if implemented improperly or if a loophole is found. WordPress nonces are designed to be used for CSRF protection, not authorization control. Implementing capability checks in conjunction with CSRF protection on sensitive functions for full verification provides protection to ensure a request is coming from an authorized user.

The Impact

As previously mentioned, several AJAX functions were affected, causing a large variety of potential impacts. A few of the most impactful actions were wp_ajax_pagelayer_save_content, wp_ajax_pagelayer_update_site_title, and wp_ajax_pagelayer_save_template.

The pagelayer_save_content function is used to save a page’s data through the page builder. The lack of permission checks on this function allowed authenticated users, regardless of permissions, the ability to change any data on a page edited with PageLayer.

An attacker could wipe the pages completely or inject any content they would like on the site’s pages and posts. In addition, a few widgets allowed Javascript to be injected, including the “Button” widget. There is no sanitization on the “Button” widget’s text, which allows for malicious Javascript to be used as a text. This Javascript would execute once any user browsed to a page containing that button.

The pagelayer_update_site_title function is used to update a site’s title. The lack of permission checks on this function allowed authenticated users the ability to change a site title to any title of their choosing. Though less detrimental, this could still affect your sites search engine ranking if unnoticed for an extended period of time.

The pagelayer_save_template function is used to save PageLayer templates for the PageLayer Theme Builder. The lack of permission checks on this function allowed authenticated users the ability to create new PageLayer templates that were saved as new posts.

Though this function was intended to be used in the PRO version of the plugin, the function could still be executed in the free version, affecting all 200,000+ users of the PageLayer plugin. An attacker could create a new template, which created a new page on the site, and inject malicious Javascript in the same way they could with the pagelayer_save_content function.

Malicious Javascript can be used to inject new administrative users, redirect site visitors, and even exploit a site’s user’s browser to compromise their computer.

The Patch

In the latest version of the plugin, the developers implemented permissions checks on all of the sensitive functions that could make changes to a site, and reconfigured the plugin to create separate nonces for the public and administrative areas of a WordPress site.

The PageLayer plugin registers a settings area where configuration changes can be made. This includes functionality such as where the editor is enabled, basic content settings, basic information configurations, and more.

The settings update function used a capability check to verify that a user attempting to make any changes had the appropriate permissions. However, there was no CSRF protection to verify the legitimacy of any request attempting to update a site’s settings. This made it possible for attackers to trick an administrator into sending a request to update any of the PageLayer settings.

The “Information” tab in the settings area provides site owners with a way to set a default address, telephone number, and contact email address that are displayed whenever the corresponding widgets were used on a page. There was no sanitization on the address or telephone number settings, and due to the administrator’s capability to use unfiltered_html, Javascript could be injected into these settings.

The Impact

This allowed attackers the ability to inject malicious scripts while exploiting the CSRF vulnerability in the settings. If the widget was already enabled, any injected malicious scripts would execute whenever someone browsed to a page containing that widget. If the widget was not yet enabled, the malicious scripts could be executed once an administrator started editing and inserting the widget into a page. As always, these scripts can do things like create a new administrative account and redirect users to malicious sites.

The Patch

In the patched version of the plugin, the developers implemented CSRF protection consisting of a WordPress nonce and verification of that nonce when updating settings.

PoC Walkthrough: pagelayer_save_content

Disclosure Timeline

Conclusion

In today’s post, we detailed several flaws related to unprotected AJAX actions and nonce disclosure that allowed for attackers to make several malicious modifications to a site’s pages and posts in addition to providing attackers with the ability to inject malicious Javascript. These flaws have been fully patched in version 1.1.2. We recommend that users immediately update to the latest version available, which is version 1.1.4 at the time of this publication.

Sites running Wordfence Premium have been protected from attacks against this vulnerability since April 30, 2020. Sites running the free version of Wordfence will recieve this firewall rule update on May 30, 2020. If you know a friend or colleague who is using this plugin on their site, we highly recommend forwarding this advisory to them to help keep their sites protected.

Between May 29 and May 31, 2020, the Wordfence Firewall blocked over 130 million attacks intended to harvest database credentials from 1.3 million sites by downloading their configuration files.

The peak of this attack campaign occurred on May 30, 2020. At this point, attacks from this campaign accounted for 75% of all attempted exploits of plugin and theme vulnerabilities across the WordPress ecosystem.

Different vulnerabilities, same IPs

The previously reported XSS campaigns sent attacks from over 20,000 different IP addresses. The new campaign is using the same IP addresses, which accounted for the majority of the attacks and sites targeted. This campaign is also attacking nearly a million new sites that weren’t included in the previous XSS campaigns.

As with the XSS campaigns, almost all of the attacks are targeted at older vulnerabilities in outdated plugins or themes that allow files to be downloaded or exported. In this case the attackers are attempting to download wp-config.php, a file critical to all WordPress installations which contains database credentials and connection information, in addition to authentication unique keys and salts. An attacker with access to this file could gain access to the site’s database, where site content and users are stored.

Indicators of Compromise

Attacks by this campaign should be visible in your server logs. Look for any log entries containing wp-config.php in the query string that returned a 200 response code.

The top 10 attacking IP addresses in this campaign are listed below.

What should I do?

Sites running Wordfence are protected against this campaign. If your site is not running Wordfence, and you believe you have been compromised, change your database password and authentication unique keys and salts immediately.

If your server is configured to allow remote database access, an attacker with your database credentials could easily add an administrative user, exfiltrate sensitive data, or delete your site altogether. Even if your site does not allow remote database access, an attacker who knows your site’s authentication keys and salts may be able to use them to more easily bypass other security mechanisms.

If you’re not comfortable making the changes above, please contact your host, since changing your database password without updating the wp-config.php file can temporarily take down your site.

Conclusion

In today’s post, we covered another large-scale attack campaign against WordPress sites by a threat actor we have been tracking since February. All Wordfence users, including sites running the free version of Wordfence, and Wordfence Premium, are protected against these attacks. Nonetheless, we urge you to make sure that all plugins and themes are kept up to date, and to share this information with any other site owners or administrators you know. Attacks by this threat actor are evolving and we will continue to share additional information as it becomes available.

WordPress Core version 5.4.2 has just been released. Since this release is marked as a combined security and bug fix update, we recommend updating as soon as possible. With that said, most of the security fixes themselves are for vulnerabilities that would require specific circumstances to exploit. All in all this release contains 6 security fixes, 3 of which are for XSS (Cross-Site Scripting) vulnerabilities. Both the free and Premium versions of Wordence have robust built-in XSS protection which will protect against potential exploitation of these vulnerabilities.

A Breakdown of each security issue

An XSS issue where authenticated users with low privileges are able to add JavaScript to posts in the block editor

This flaw would have made it possible for an attacker to inject JavaScript into a post by manipulating the attributes of Embedded iFrames. This would be exploitable by users with the edit_posts capability, meaning users with the Contributor role or higher in most configurations.

This issue was discovered and reported by Sam Thomas (jazzy2fives)

An XSS issue where authenticated users with upload permissions are able to add JavaScript to media files

This flaw would have made it possible for an attacker to inject JavaScript into the “Description” field of an uploaded media file. This would be exploitable by users with the upload_files capability, meaning users with the Author role or higher in most configurations.

This issue was discovered and reported by Luigi – (gubello.me)

An open redirect issue in wp_validate_redirect()

For this flaw, the wp_validate_redirect function failed to sufficiently sanitize URLs supplied to it. As such it would have been possible under certain circumstances for an attacker to craft a link to an impacted site that would redirect visitors to a malicious external site. This would not require specific capabilities, but it would typically require either social engineering or a separate vulnerability in a plugin or theme to exploit.

This issue was discovered and reported by Ben Bidner of the WordPress Security Team.

An authenticated XSS issue via theme uploads

This flaw would have made it possible for an attacker to inject JavaScript into the stylesheet name of a broken theme, which would then be executed if another user visited the Appearance->Themes page on the site. This would be exploitable by users with the install_themes or edit_themes capabilities, which are only available to administrators in most configurations.

This issue was discovered and reported by Nrimo Ing Pandum

An issue where set-screen-option can be misused by plugins leading to privilege escalation

For this flaw, a plugin incorrectly using the set-screen-option filter to save arbitrary or sensitive options could potentially be used by an attacker to gain administrative access. We are not currently aware of any plugins that are vulnerable to this issue.

This issue was discovered and reported by Simon Scannell of RIPS Technologies

An issue where comments from password-protected posts and pages could be displayed under certain conditions

For this flaw, comment excerpts on password-protected posts could have been visible on sites displaying the “Recent Comments” widget or using a plugin or theme with similar functionality.

This issue was discovered and reported by Carolina Nymark

Note: This is unrelated to an issue where unmoderated spam comments were briefly visible and indexable by search engines.

What should I do?

Most of these vulnerabilities appear to be exploitable only under limited circumstances or by trusted users, but we recommend updating as soon as possible. Attackers may find ways to exploit them more easily, or the researchers who discovered these vulnerabilities may publish Proof of Concept code that allows simpler exploitation. This is a minor WordPress release, so most sites will automatically update to the new version.

Conclusion

We’d like to thank the WordPress core team and the researchers who discovered and responsibly reported these vulnerabilities for making WordPress safer for everyone.

You can find the official announcement of the WP 5.4.2 release on this page. If you have any questions or comments, please don’t hesitate to post them below and we’ll do our best to answer them in a timely manner. If you are one of the researchers whose work is included above and would like to provide additional detail or corrections, we welcome your comments.