CVE-2026-76579: litespeedtech litespeed_cache Cross-site Scripting

Vulnerability summary

CVE-2026-76579 is a medium (CVSS 4.7) Cross-site Scripting vulnerability in litespeedtech litespeed_cache. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 30.1% of scored vulnerabilities.

Timeline

1. 19-09-2026
   PublishedVulnerability first disclosed.
2. 19-09-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.