Stored XSS in W3 Total Cache WordPress Plugin

Executive Summary

This is a Stored Cross-Site Scripting (XSS) vulnerability in the W3 Total Cache WordPress plugin up to version 2.10.5. It occurs due to insufficient input sanitization and output escaping in the LazyLoad Background Mutator feature. Unauthenticated attackers can inject malicious scripts into comment content, which execute when users view the affected page. The attack requires the Lazy Load Images feature with Process background images enabled and the malicious comment to be approved by a moderator.

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Detection Guidance

Check if the W3 Total Cache plugin is installed and its version is up to 2.10.5. Inspect comments for malicious scripts in WordPress. Enable plugin logging if available to track suspicious activity.

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Impact Analysis

If you use the affected W3 Total Cache plugin, attackers could inject malicious scripts into your website through comments. These scripts could steal user data, hijack sessions, or deface your site. Users visiting your site might have their browsers compromised, leading to further attacks or data breaches.

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Compliance Impact

This vulnerability could lead to unauthorized access to user data, violating GDPR and HIPAA requirements for data protection and privacy. If exploited, it may result in data breaches, triggering mandatory breach notifications and potential fines under these regulations.

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Mitigation Strategies

Update the W3 Total Cache plugin to the latest version beyond 2.10.5. Disable the Lazy Load Images feature with Process background images if enabled. Review and remove any suspicious comments awaiting moderation.

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