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Vulnerability record · CVE-2026-18978 · published 28 August 2026

CVE-2026-18978: Cross-site scripting vulnerability

The LiteSpeed Cache plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Comment Content in all versions up to, and including, 7.8.1 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. A comment payload crafted exclusively from decimal numeric character references (e.g. ", <, >) placed inside an allowed element such as <code> bypasses WordPress's wp_kses sanitization, as kses does not treat a data-settings="..." substring within text content as an HTML attribute, allowing the malicious payload to reach the vulnerable function. For this to be exploitable, the site must allow users with previously approved comments to write new comments, and the require_name_email setting must be disabled.

7.2 CVSS 3.1 High EPSS 0.37% · top 72.0% CWE-79 · Cross-site scripting Deferred
7.2CVSS 3.1 base score
0.37%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
7References
28 Aug 2026Last modified by NVD

Description

The LiteSpeed Cache plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Comment Content in all versions up to, and including, 7.8.1 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. A comment payload crafted exclusively from decimal numeric character references (e.g. ", <, >) placed inside an allowed element such as <code> bypasses WordPress's wp_kses sanitization, as kses does not treat a data-settings="..." substring within text content as an HTML attribute, allowing the malicious payload to reach the vulnerable function. For this to be exploitable, the site must allow users with previously approved comments to write new comments, and the require_name_email setting must be disabled.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

References

LinkTags
https://plugins.trac.wordpress.org/browser/litespeed-cache/trunk/src/media.cls.php#L1317
https://plugins.trac.wordpress.org/browser/litespeed-cache/trunk/src/media.cls.php#L1358
https://plugins.trac.wordpress.org/browser/litespeed-cache/trunk/src/media.cls.php#L1405
https://plugins.trac.wordpress.org/browser/litespeed-cache/trunk/src/media.cls.php#L777
https://plugins.trac.wordpress.org/changeset/3635849/litespeed-cache/trunk/src/media.cls.php
https://plugins.trac.wordpress.org/changeset?old_path=%2Flitespeed-cache/tags/7.8.1&new_path=%2Flitespeed-cache/tags/7.9
https://www.wordfence.com/threat-intel/vulnerabilities/id/0b045f3d-8412-4e35-b369-2b485639274d?source=cve

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Source: NIST National Vulnerability Database (record CVE-2026-18978), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.