CVE-2026-8489 in Ultimate Member Plugin
Summary
by MITRE • 07/03/2026
The Ultimate Member – User Profile, Registration, Login, Member Directory, Content Restriction & Membership Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'about_me' parameter in all versions up to, and including, 2.11.4 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with subscriber-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 07/04/2026
The Ultimate Member plugin for WordPress represents a comprehensive membership solution that handles user profiles, registration processes, login systems, member directories, and content restriction mechanisms. This plugin has been identified with a critical stored cross-site scripting vulnerability affecting all versions up to and including 2.11.4, which poses significant security risks to WordPress installations relying on this membership framework. The vulnerability specifically resides within the handling of the 'about_me' parameter, making it particularly concerning given that this field is commonly used for user-generated content in profile management systems.
The technical flaw stems from inadequate input sanitization and insufficient output escaping mechanisms within the plugin's codebase. When authenticated users with subscriber-level access or higher submit data containing malicious scripts through the about_me parameter, the plugin fails to properly validate or sanitize this input before storing it in the database. Subsequently, when other users access pages containing this stored malicious content, the unescaped scripts execute in their browsers, creating a persistent cross-site scripting attack vector. This vulnerability operates under the CWE-79 classification as a classic stored XSS flaw, where malicious code is permanently stored on the target server and executed whenever the compromised page is accessed.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers to perform various malicious activities including session hijacking, credential theft, redirection to malicious sites, and data exfiltration. Since the attack requires only subscriber-level privileges, it represents a significant risk for WordPress sites where user registration is open or where subscribers have access to profile editing functionality. The vulnerability allows threat actors to establish persistent footholds within the application, potentially leading to full compromise of user accounts and administrative access if attackers can escalate their privileges through additional means.
Security practitioners should immediately implement mitigations including upgrading to the latest plugin version where the vulnerability has been patched, implementing input validation at multiple layers, and applying output escaping mechanisms for all user-generated content. Organizations should also consider implementing web application firewalls with XSS detection capabilities and conducting regular security audits of WordPress plugins to identify similar vulnerabilities. The ATT&CK framework categorizes this vulnerability under T1566 - Phishing and T1071.004 - Application Layer Protocol: DNS, as attackers can use such vulnerabilities to establish persistent access points and potentially escalate privileges within the WordPress environment. Additionally, implementing principle of least privilege for user roles and regular security monitoring of user profile modifications can significantly reduce the risk exposure associated with this stored XSS vulnerability.