What the vulnerability does
01Description
The LiteSpeed Cache plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the /wp-json/litespeed/v1/notify_ccss and /wp-json/litespeed/v1/notify_ucss REST API endpoints in all versions up to, and including, 7.7. These endpoints accept CSS content from QUIC.cloud callback notifications and store it to disk without sanitization. The stored content is later rendered inline frontend page loads without output escaping. The access control protecting these endpoints is IP-based validation that can potentially be bypassed when the WordPress site is deployed behind a reverse proxy, load balancer, or CDN with certain configurations. This makes it possible for unauthenticated attackers, under certain conditions, to inject arbitrary JavaScript into CCSS/UCSS content.
Explanation of Vulnerability in Simple Terms
02Summary
LiteSpeed Cache versions 7.7 and earlier contain a cross-site scripting (XSS) vulnerability that allows attackers to inject malicious scripts affecting multiple users. The vulnerability requires no authentication or user interaction and can impact confidentiality and integrity across the affected site. Site administrators should update to a version newer than 7.7.
What an attacker can do
03Attacker Capabilities
Inject malicious JavaScript that executes in other users' browsers and affects site data.
Potential impact on your site
04Site Impact
Visitors and administrators may have malicious scripts run in their browsers, risking credential theft or site defacement.
Conditions required to exploit
05Prerequisites
Network access to the site; no authentication or user interaction required.
Key dates
06Disclosure timeline
May 27, 2026
CVE published
May 27, 2026
Record updated
