---
id: CVE-2026-76579
title: >-
  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
summary: >-
  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…
severity: medium
cvss: 4.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: litespeedtech
product: LiteSpeed Cache
affected:
  - litespeed_cache <= 7.9
published: '2026-09-19'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T13:33:33.387'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-76579'
references:
  - url: >-
      https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L566
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L591
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L617
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php#L855
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/changeset/3676856/litespeed-cache/trunk/src/esi.cls.php
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/changeset?reponame=&new=3676856%40litespeed-cache%2Ftags%2F7.9.1&old=3635849%40litespeed-cache%2Ftags%2F7.9
    label: security@wordfence.com
  - url: >-
      https://www.wordfence.com/threat-intel/vulnerabilities/id/ba236f86-0434-4030-8e14-4db3919226eb?source=cve
    label: security@wordfence.com
tags:
  - nvd
  - cve.org
epss: 0.0023
epssPercentile: 0.1411
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-19T13:17:15.684976Z'
ingestedAt: '2026-09-19T09:00:39.470Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.