W3 Total Cache <= 2.10.7 - Unauthenticated Stored Cross-Site Scripting via Comment Content Cached as HTML after License Expiry

Summary

The W3 Total Cache plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'comment' parameter in all versions up to, and including, 2.10.7 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. Exploitation requires that a Pro license was previously active with REST caching enabled and has since become inactive while Disk Enhanced page caching remains configured, and that the attacker holds a previously approved commenter identity.

Remediation

1. Inventory every boldgrid W3 Total Cache deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Referencehttps://github.com/BoldGrid/w3-total-cache/commit/7168b0d7cc80e827ad234a0428ab3ecdbef3c107
• Referencehttps://plugins.trac.wordpress.org/browser/w3-total-cache/tags/2.10.7/Licensing_Plugin_Admin.php#L928
• Referencehttps://plugins.trac.wordpress.org/browser/w3-total-cache/tags/2.10.7/PgCache_ContentGrabber.php#L1450
• Referencehttps://plugins.trac.wordpress.org/browser/w3-total-cache/tags/2.10.7/PgCache_ContentGrabber.php#L1719
• Referencehttps://plugins.trac.wordpress.org/changeset/3757452/w3-total-cache/trunk/PgCache_ContentGrabber.php
• Referencehttps://www.wordfence.com/threat-intel/vulnerabilities/id/0169909e-c6cd-4d08-8301-5e09fce4429c?source=cve