Unauthenticated Stored XSS in Ultimate Member WordPress Plugin

Mitigation Strategies

To mitigate this vulnerability, you should update the Ultimate Member WordPress plugin to version 2.12.0 or later, where the issue has been fixed.

Additionally, restrict the ability to add or edit custom textarea profile fields to trusted users only, and consider reviewing user profiles for suspicious JavaScript code injections.

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Executive Summary

The vulnerability CVE-2026-11766 affects the Ultimate Member WordPress plugin versions prior to 2.12.0. It is a stored Cross-Site Scripting (XSS) issue where custom textarea profile fields are not properly sanitized or escaped before being displayed on user profiles.

This flaw allows authenticated users with Subscriber-level access or higher to inject malicious JavaScript code into these profile fields. When any user, including administrators, views the affected profile, the injected JavaScript executes.

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Impact Analysis

This vulnerability can lead to unauthorized execution of malicious JavaScript code within the context of the affected website.

• Attackers with Subscriber-level access can inject scripts that run when profiles are viewed.
• Malicious scripts could steal sensitive information, hijack user sessions, or perform actions on behalf of users, including administrators.
• It poses a high security risk, potentially compromising the integrity and confidentiality of the website and its users.

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Compliance Impact

The vulnerability allows authenticated users to inject and execute malicious JavaScript code on user profiles, which can lead to unauthorized access or manipulation of user data.

Such a security flaw can impact compliance with standards like GDPR and HIPAA, which require protection of personal data and prevention of unauthorized access or data breaches.

Specifically, stored Cross-Site Scripting (XSS) vulnerabilities can be exploited to steal sensitive information, perform actions on behalf of users, or compromise administrative accounts, all of which violate data protection and privacy requirements.

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