CVE-2026-108491 in Everest Forms Plugin
Summary
by MITRE • 10/15/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Everest Forms Everest Forms everest-forms allows Stored XSS.This issue affects Everest Forms: from n/a through 3.6.1.
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Analysis
by VulDB Data Team • 10/15/2026
The identified security flaw represents a classic instance of Improper Neutralization of Input During Web Page Generation, commonly known as Cross-Site Scripting or XSS. Specifically, this vulnerability manifests as a Stored XSS within the Everest Forms plugin for WordPress, affecting versions ranging from its initial release through version 3.6.1. Unlike reflected XSS attacks where malicious scripts are executed via manipulated URLs, stored vulnerabilities pose a more severe risk because the injected payload is permanently saved on the target server. In the context of web forms, this typically occurs when user-supplied data submitted through form fields is not adequately sanitized or validated before being processed and subsequently rendered in HTML responses for other users.
The technical root cause lies in the application's failure to properly neutralize special characters that have meaning within an HTML document environment. When a victim submits a form containing malicious JavaScript code, such as script tags or event handlers like onerror, the backend system accepts this input without applying sufficient escaping mechanisms. Consequently, when another user views the page displaying the submitted form data, their browser interprets and executes the embedded script in the context of the vulnerable website's domain. This behavior aligns directly with CWE-79, which defines improper neutralization of input during web page generation as a critical weakness allowing attackers to inject client-side scripts into web pages viewed by other users.
The operational impact of this vulnerability is significant due to its persistent nature and broad potential audience. An attacker can craft a malicious form submission that remains active on the server indefinitely, meaning every subsequent visitor who loads the affected page becomes a potential victim without needing any further interaction from the attacker beyond the initial setup. This persistence allows for prolonged access to sensitive information stored in browser cookies or session tokens, potentially leading to account takeover if authentication credentials are stolen. Furthermore, attackers can use this vector to deface websites by altering displayed content, redirect users to malicious phishing sites designed to harvest additional credentials, or distribute malware through drive-by download techniques that exploit vulnerabilities in the victim's web browser or plugins.
From a threat intelligence perspective, this vulnerability maps closely to MITRE ATT&CK technique T1059, specifically sub-technique 007 which covers JavaScript execution. The attack chain typically involves initial access via social engineering or direct submission of the malicious form, followed by script injection and eventual exploitation for data exfiltration or session hijacking. Because Everest Forms is a widely used plugin in the WordPress ecosystem, the scale of potential impact extends across numerous websites that rely on this tool for contact forms, surveys, and registration processes, amplifying the risk to both site administrators and end-users interacting with these digital interfaces.
To mitigate this vulnerability, immediate action must be taken by upgrading the Everest Forms plugin to a version later than 3.6.1 where the input validation logic has been corrected. Developers should ensure that all user inputs are strictly validated against expected data types and formats before processing. Furthermore, output encoding is critical; any dynamic content rendered in HTML contexts must have special characters such as ampersands, less-than signs, greater-than signs, quotes, and apostrophes encoded using appropriate functions like htmlspecialchars with the ENT_QUOTES flag and UTF-8 charset. Implementing a Content Security Policy (CSP) header can also serve as an effective defense-in-depth measure by restricting the sources from which scripts are allowed to execute, thereby neutralizing many XSS attacks even if input sanitization fails partially. Regular security audits and penetration testing of form handling logic should be conducted to identify similar weaknesses in other parts of the application architecture.