Authentication Bypass in Simple Membership Plugin

Executive Summary

The Simple Membership plugin for WordPress has an authentication bypass flaw in versions up to 4.8.0. It allows unauthenticated attackers to take over Administrator accounts on child sites in a Multisite network by registering with a victim's username and email, then changing the victim's password through profile edits.

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Detection Guidance

Check if the Simple Membership plugin is installed and verify its version. If it is version 4.8.0 or lower, the system is vulnerable. Use WordPress admin dashboard or run: wp plugin list --name=simple-membership to check the version.

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Impact Analysis

Attackers could gain full control over your WordPress site's administrator account, allowing them to install malicious software, steal data, or disrupt operations. This is especially risky if public registration is enabled on your site.

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Compliance Impact

This vulnerability could lead to unauthorized access to administrator accounts, potentially exposing sensitive user data. For GDPR, this may result in unauthorized processing or disclosure of personal data, violating principles of lawfulness and security. For HIPAA, it could allow unauthorized access to protected health information, compromising confidentiality requirements.

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Mitigation Strategies

Update the Simple Membership plugin to version 4.8.1 or higher immediately. Disable public registration if not needed. Review user accounts for unauthorized Administrator role assignments.

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