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CVE-2026-18109: W3 Total Cache <= 2.10.3 - Unauthenticated Stored Cross-Site Scripting via Comment Author Name

• Severity: high (CVSS 7.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-14 · updated 2026-08-14
• Weakness: CWE-79

Description

The W3 Total Cache plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Comment Author Name in all versions up to, and including, 2.10.3 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. This vulnerability is only exploitable when the Lazy Load Images feature of W3 Total Cache is enabled, as the unsafe re-emission occurs exclusively within the LazyLoad mutator's img tag rewriting step.

Affected products

• boldgrid W3 Total Cache: through 2.10.3

References

• https://plugins.trac.wordpress.org/browser/w3-total-cache/tags/2.10.2/UserExperience_LazyLoad_Mutator.php#L162
• https://plugins.trac.wordpress.org/browser/w3-total-cache/tags/2.10.2/UserExperience_LazyLoad_Mutator.php#L403
• https://plugins.trac.wordpress.org/browser/w3-total-cache/tags/2.10.2/UserExperience_LazyLoad_Mutator.php#L85
• https://plugins.trac.wordpress.org/browser/w3-total-cache/tags/2.10.2/UserExperience_LazyLoad_Plugin.php#L116
• https://plugins.trac.wordpress.org/changeset/3635675/w3-total-cache/trunk/UserExperience_LazyLoad_Mutator.php
• https://plugins.trac.wordpress.org/changeset?old_path=%2Fw3-total-cache/tags/2.10.3&new_path=%2Fw3-total-cache/tags/2.10.4
• https://plugins.trac.wordpress.org/changeset?reponame=&new=3635675%40w3-total-cache%2Ftags%2F2.10.4&old=3625062%40w3-total-cache%2Ftags%2F2.10.3
• https://www.wordfence.com/threat-intel/vulnerabilities/id/16ac73ae-6a0a-4c9b-8830-e0745061e587?source=cve

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