The Importance of Regular WordPress Maintenance: A Case Study of Gravity Forms Plugin Vulnerability

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June 3, 2023

WordPress, a widely used content management system, is known for its flexibility and ease of use. However, with flexibility comes responsibility. The recent vulnerability discovered in the popular WordPress plugin, Gravity Forms, serves as a stark reminder of the importance of regular WordPress maintenance.

Gravity Forms: A Widely Used Plugin

Gravity Forms is a premium WordPress plugin that is currently used by over 930,000 websites. It’s a custom form builder that website owners use for creating various forms required for visitor-site interactions or transactions. The plugin is used by a wide variety of large companies, including Airbnb, ESPN, Nike, NASA, PennState, and Unicef.

The Vulnerability: PHP Object Injection

Recently, a vulnerability was discovered in Gravity Forms by PatchStack. The vulnerability, known as CVE-2023-28782, affects all plugin versions from 2.73 and below. The flaw was discovered on March 27, 2023, and fixed by the vendor with the release of version 2.7.4 on April 11, 2023.

The issue arises from the lack of user-supplied input checks for the ‘maybe_unserialize’ function and can be triggered by submitting data to a form created with Gravity Forms. This could result in an arbitrary PHP object(s) injection into the application scope.

The Impact and Mitigation

The potential severity of CVE-2023-28782 is somewhat mitigated if no significant POP (property-oriented programming) chain is found in the vulnerable plugin. However, the risk remains severe if the same site uses other plugins or themes that contain a POP chain. In such cases, exploitation of CVE-2023-28782 could lead to arbitrary file access and modification, user/member data exfiltration, code execution, and more.

The plugin vendor fixed the flaw by removing the use of the ‘maybe_unserialize’ function from the Gravity Forms plugin in version 2.74.

The Importance of Regular WordPress Maintenance

This incident underscores the importance of regular WordPress maintenance. Website administrators using Gravity Forms were advised to apply the available security update as soon as possible. It is also crucial to apply any updates across all plugins and themes active on your WordPress site, as security fixes may eliminate attack vectors, like POP chains, that could be leveraged in this case to launch damaging attacks.

The Gravity Forms vulnerability serves as a wake-up call for all WordPress website owners. Regular maintenance, including timely updates of all plugins and themes, is not just a best practice—it’s a necessity. By staying vigilant and proactive, website owners can protect their sites from potential threats and ensure a secure online experience for their users.