MSRXCVE-2026-76579
CVE-2026-76579
LiteSpeed Cache <= 7.9 - Reflected Cross-Site Scripting via ESI 'esi' Parameter
CVSS 3.1 · CNA · wordfence.com
chance of exploitation in the next 30 days (EPSS; higher than 31% of CVEs)
The LiteSpeed Cache plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'esi' parameter in all versions up to, and including, 7.9 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Exploitation requires that the attacker supply a validly signed 'esi' value in the GET query string while submitting a separate attacker-controlled 'esi' payload as a POST body field, relying on PHP's default $_REQUEST merge order to have the POST value take precedence at the point of execution.
Scores
Affected products
- litespeedtech LiteSpeed Cache: 0 to ≤ 7.9
Weakness: CWE-79
7 references (advisories, patches, write-ups)
- https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L566
- https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L591
- https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L617
- https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L855
- https://plugins.trac.wordpress.org/changeset/3676856/litespeed-cache/trunk/src/esi.cls.php
- https://plugins.trac.wordpress.org/changeset?reponame=&new=3676856%40litespeed-cache%2Ftags%2F7.9.1&old=3635849%40litespeed-cache%2Ftags%2F7.9
- https://www.wordfence.com/threat-intel/vulnerabilities/id/ba236f86-0434-4030-8e14-4db3919226eb?source=cve
Sources: NVD, CVE.org, FIRST EPSS. Missing ones did not answer or have no record yet.