Stored XSS in Ultimate Member Plugin User Description Field

Executive Summary

This vulnerability is a Stored Cross-Site Scripting (XSS) issue in the Ultimate Member WordPress plugin, specifically in the user description field. It occurs because the plugin does not properly sanitize or escape input and output when HTML support for user descriptions is enabled. Authenticated users with subscriber-level access or higher can inject malicious scripts into user description fields, which then execute whenever someone views the affected page.

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Impact Analysis

The vulnerability allows attackers with subscriber-level access to inject arbitrary web scripts into user description fields. These scripts execute in the browsers of users who view the injected pages, potentially leading to unauthorized actions such as stealing session cookies, defacing content, or performing actions on behalf of other users without their consent.

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Detection Guidance

This vulnerability involves Stored Cross-Site Scripting (XSS) via the user description field in the Ultimate Member WordPress plugin when HTML support for user descriptions is enabled.

To detect this vulnerability on your system, you can check if your WordPress installation uses the Ultimate Member plugin version 2.11.1 or earlier with HTML support enabled for user descriptions.

You can also look for suspicious or unexpected HTML or script tags in user description fields in the database or on user profile pages.

• Use SQL queries to search the WordPress database for user descriptions containing script tags, for example: SELECT ID, user_description FROM wp_usermeta WHERE user_description LIKE '%<script>%';
• Use curl or wget commands to fetch user profile pages and inspect the HTML output for injected scripts.
• Use web vulnerability scanners that support detection of stored XSS vulnerabilities in WordPress plugins.

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Mitigation Strategies

The primary immediate mitigation step is to upgrade the Ultimate Member plugin to version 2.11.2 or later, where the vulnerability has been fixed by removing HTML support in user descriptions and improving input sanitization.

If upgrading immediately is not possible, disable the "HTML support for user description" setting in the Ultimate Member plugin to prevent exploitation.

Review and sanitize existing user descriptions to remove any malicious scripts or HTML content.

Monitor user accounts with subscriber level access and above for suspicious activity or injected scripts.

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Compliance Impact

The vulnerability in the Ultimate Member WordPress plugin allows authenticated users to inject arbitrary web scripts via the user description field, which can lead to stored cross-site scripting (XSS) attacks.

Such vulnerabilities can potentially impact compliance with common standards and regulations like GDPR and HIPAA because they may lead to unauthorized access or manipulation of user data, compromising data integrity and confidentiality.

Specifically, GDPR requires organizations to protect personal data against unauthorized processing and breaches, while HIPAA mandates safeguarding protected health information. An XSS vulnerability could be exploited to steal or alter sensitive information, thus violating these requirements.

However, the provided information does not explicitly state the direct compliance impact or any regulatory assessment related to this vulnerability.

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