Everest Forms is a widely used plugin to create forms on websites powered by WordPress. It is used by various businesses and individuals to manage contact forms, surveys, and other user-input features. Everest Forms offers an intuitive interface and drag-and-drop form builder for easy form creation. Companies leverage this plugin for its ease of use, adaptability to different industries, and general accessibility to WordPress users. It is especially popular among users who need a flexible form system that does not require deep technical understanding. The continuous updates and large community support make it a go-to choice for WordPress users seeking form-related functionalities.
The vulnerability detected in the Everest Forms plugin involves PHP Object Injection through deserialization of untrusted input. This security flaw allows attackers to execute arbitrary PHP code by exploiting the deserialization functions embedded within the plugin's core code. It specifically affects inputs from form entry metadata that are not securely handled. Without passing the allowed_classes parameter during unserialization, the plugin can inadvertently execute malicious payloads injected by unauthorized users. This vulnerability is severe, as it provides a vector for privilege escalation and complete compromise of the affected site.
The technical intricacies of the vulnerability lie within how the plugin processes form entries. Attackers can inject payloads using serialized PHP objects via any public form field. The vulnerable file in this plugin is html-admin-page-entries-view.php where entries are unserialized without class filtering. When an administrator reviews form entries, the malicious payloads activate if sanitize_text_field() fails to strip essential serialization control characters. This design flaw allows untrusted data to be stored and later processed unsafely, posing major security risks on systems using vulnerable plugin versions.
Exploiting this vulnerability could lead to severe consequences including full control over the affected site by arbitrary code execution. Attackers might alter site content, steal sensitive information, disrupt services, or launch further attacks from the compromised server. Since it can allow unauthorized administrative access, it damages the website's confidentiality, integrity, and availability significantly. This impact necessitates immediate mitigation actions to secure systems relying on this plugin to prevent potential data breaches or site takeovers.
REFERENCES
- Update the Everest Forms plugin to a version newer than 3.4.3 immediately.
- Regularly audit any third-party plugins for security patches or updates.
- Implement web application firewalls (WAF) to detect and block suspicious deserialization attempts.
- Limit access to WordPress administrative sections to authorized personnel only.
- Consistently monitor logs for unusual administrative activities.
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