Executive brief
The LiteSpeed Cache plugin for WordPress contains a reflected cross-site scripting vulnerability that allows attackers to inject malicious scripts into web pages. An attacker must trick users into clicking a specially crafted link to execute the injected script in their browser, potentially stealing session data or performing unauthorized actions on their WordPress site.
Technical details
The vulnerability exists in the ESI (Edge Side Includes) parameter handling due to insufficient input sanitization and output escaping. An attacker can supply a validly signed GET 'esi' parameter along with an attacker-controlled POST 'esi' payload; PHP's default $_REQUEST merge order causes the POST value to take precedence, bypassing signature validation and allowing arbitrary script injection on unauthenticated page loads.
Affected products
- LiteSpeed Cache up to and including 7.9
Timeline
- 2026-09-19: disclosed