Authenticated User Privilege Escalation in Advanced Twenty Seventeen WordPress Plugin

Executive Summary

This vulnerability in the Advanced Twenty Seventeen WordPress plugin allows any authenticated user, including low-privilege subscribers, to switch the active theme of the site without proper authorization. The plugin fails to perform capability or nonce checks on the action that creates and activates a child theme, enabling unauthorized theme changes.

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Detection Guidance

Check if the Advanced Twenty Seventeen plugin version 1.3.1 or earlier is installed. Look for unauthorized theme switches in WordPress logs or admin activity. Monitor for CSRF attempts targeting the ats_create_child_theme action.

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Impact Analysis

An attacker could exploit this to change the site's theme, potentially disrupting functionality, exposing sensitive data, or defacing the website. Since it can be triggered via CSRF, an attacker could trick an administrator into unknowingly switching themes by visiting a malicious link.

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Compliance Impact

This vulnerability could lead to unauthorized changes in the website's appearance or functionality, potentially exposing user data or violating compliance requirements. For GDPR, unauthorized access may result in data breaches. For HIPAA, it could compromise protected health information if the site handles such data.

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Mitigation Strategies

Update the Advanced Twenty Seventeen plugin to the latest version immediately. Remove or disable the plugin if no update is available. Implement strict capability checks and nonce validation for all admin actions.

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