CVE-2026-11766
Summary
by MITRE • 07/06/2026
The Ultimate Member WordPress plugin before 2.12.0 does not properly sanitise and escape the value of custom textarea profile fields before outputting it on user profiles, allowing authenticated users with Subscriber-level access and above to store JavaScript that executes when any user, including an administrator, views the affected profile.
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Analysis
by VulDB Data Team • 07/06/2026
The vulnerability exists within the Ultimate Member WordPress plugin version 2.11.9 and earlier, where custom textarea profile fields fail to implement proper sanitization and escaping mechanisms before rendering output on user profiles. This flaw represents a classic cross-site scripting vulnerability that allows authenticated attackers with subscriber-level privileges or higher to inject malicious javascript code into profile fields. The issue stems from insufficient input validation and output encoding practices within the plugin's profile field handling system, creating an environment where malicious payloads can persist and execute when any user accesses the compromised profile page.
The technical exploitation occurs through the manipulation of textarea profile fields that are designed to accept rich text content. When an attacker with subscriber privileges or higher creates or modifies a custom textarea field containing javascript code, the plugin fails to sanitize this input before displaying it on the user profile page. This vulnerability operates at the application layer and specifically affects the output rendering process where user-generated content is displayed without proper context-aware escaping mechanisms. The attack vector relies on the principle that the plugin does not distinguish between legitimate content and potentially malicious script code during the display phase, allowing arbitrary javascript execution in the context of any user viewing the affected profile.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it can enable attackers to perform privilege escalation activities, steal session cookies, redirect users to malicious sites, or execute additional attacks through the compromised user's browser. When administrators or other high-privilege users view profiles containing malicious code, their browsers execute the injected javascript in the context of their authenticated sessions, potentially leading to complete account compromise and further network infiltration. This vulnerability particularly affects organizations relying on Ultimate Member for user management where profile information might contain sensitive personal data or where administrators regularly review user profiles.
The flaw aligns with common weakness enumerations such as CWE-79 Cross-Site Scripting and CWE-116 Improper Output Neutralization, while also mapping to ATT&CK techniques including T1548.002 Account Manipulation and T1059.001 Command and Scripting Interpreter. Organizations should implement immediate mitigation strategies including updating to version 2.12.0 or later, which addresses the sanitization issues through proper input validation and output escaping mechanisms. Additionally administrators should consider implementing content security policies to limit script execution, monitoring user profile modifications for suspicious activity, and restricting profile field creation permissions to minimize potential attack surface. The vulnerability demonstrates the critical importance of proper input sanitization and output encoding in web applications, particularly when handling user-generated content that may be displayed across different privilege levels within a system.