CVE-2026-76579 LiteSpeed Cache <= 7.9 - Reflected Cross-Site Scripting via ESI 'esi' Parameter
Unauthenticated attackers can inject arbitrary scripts via the ESI parameter in LiteSpeed Cache, executing code in victim browsers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-76579?
CVE-2026-76579 is a medium-severity cross-site scripting vulnerability in litespeedtech LiteSpeed Cache, published on 19 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-76579?
How do I fix CVE-2026-76579?
No fix has been published for CVE-2026-76579 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-76579 being exploited?
There is no known exploitation of CVE-2026-76579 in the wild and no public exploit code.
Sources
Also known as GHSA-jf4h-cq6m-xhwf.