CVE-2026-91152 in Everest Forms Plugin
Summary
by MITRE • 10/29/2026
The Everest Forms – Contact Form, Payment Form, Quiz, Survey & Custom Form Builder with AI plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'evf_toast_type' parameter in all versions up to, and including, 3.6.2 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Exploitation requires the sibling evf_toast parameter to decode successfully via atob(), but this is a trivially attacker-controlled prerequisite.
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Analysis
by VulDB Data Team • 10/29/2026
The Everest Forms plugin for WordPress, which provides functionality for creating contact forms, payment forms, quizzes, surveys, and custom form builders with AI capabilities, contains a significant security vulnerability in versions up to 3.6.2. This flaw is classified as a Reflected Cross-Site Scripting (XSS) issue located within the evf_toast_type parameter. The root cause of this vulnerability lies in insufficient input sanitization and output escaping mechanisms during the processing of user-supplied data. Because the application fails to properly validate or encode the input before rendering it back to the browser, malicious scripts can be injected into the HTTP response stream without being neutralized by the server-side logic.
This type of vulnerability falls under the Common Weakness Enumeration category CWE-79, which describes Improper Neutralization of Input During Web Page Generation. The technical flaw allows unauthenticated attackers to craft specific URLs or form submissions that include malicious JavaScript payloads within the evf_toast_type parameter. When a victim user interacts with these crafted inputs, typically by clicking on a specially constructed link delivered through phishing or other social engineering tactics, the browser executes the injected script in the context of the vulnerable website. This execution environment grants the attacker access to sensitive information such as session cookies, authentication tokens, and potentially personally identifiable information stored within the application's local storage or cookies.
The operational impact of this vulnerability is substantial because it enables attackers to perform actions on behalf of the victim user without their knowledge or consent. By leveraging the reflected XSS vector, an adversary can redirect users to malicious sites, deface web pages, steal credentials, or even propagate malware if combined with other exploits. The requirement for a sibling parameter named evf_toast that must decode successfully via atob() presents a minor technical hurdle but remains trivially surmountable for attackers. This prerequisite simply means the attacker must ensure both parameters are present and correctly formatted in their exploit payload to trigger the vulnerability, which does not significantly reduce the overall risk profile given the ease of constructing such payloads using automated tools or simple scripting languages.
From an offensive security perspective, this vulnerability aligns with techniques observed in the MITRE ATT&CK framework, specifically under T1059 Command and Scripting Interpretation for executing arbitrary code within the browser environment, and potentially T1204 User Execution if it involves tricking users into clicking links that lead to further exploitation. The lack of proper output escaping means that any special characters or script tags included in the evf_toast_type parameter are rendered directly by the web server's response, bypassing standard security controls like Content Security Policy headers unless they are explicitly configured and enforced at a higher infrastructure level rather than within the application code itself.
To mitigate this vulnerability, immediate action is required to update the Everest Forms plugin to version 3.6.3 or later where these sanitization issues have been addressed by the developers. In cases where updating is not immediately feasible, administrators should implement web application firewall rules that detect and block requests containing suspicious patterns in the evf_toast_type parameter, such as script tags, event handlers, or encoded payloads designed to bypass basic filters. Additionally, enforcing strict Content Security Policy headers can help mitigate the impact of successful XSS attacks by restricting the sources from which scripts are allowed to execute, thereby reducing the effectiveness of injected malicious code even if it manages to reach the client side. Regular security audits and penetration testing should be conducted to identify similar input validation weaknesses in other parameters within the plugin ecosystem.