# CVE-2026-76579: LiteSpeed Cache reflected XSS via esi parameter

Source: https://junglewise.ai/threats/cve-2026-76579-the-litespeed-cache-plugin-for-wordpress-is-vulnerable-to  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-19. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-76579 · Severity: medium · CVSS 4.7 · Published 2026-09-19

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.

Technologies: [LiteSpeed Cache](https://junglewise.ai/threats/technologies/litespeed-cache-1). Vendors: [LiteSpeed](https://junglewise.ai/threats/vendors/litespeed).

## Quick answers

**Is CVE-2026-76579 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-76579 being exploited in the wild.

**How severe is CVE-2026-76579?** Medium severity, with a CVSS score of 4.7, published 19 September 2026.

**Which products and versions are affected?** LiteSpeed Cache up to and including 7.9.

**Is there a fix for CVE-2026-76579?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-76579 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-76579?** Check whether you run LiteSpeed Cache at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## 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

## References

- [https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php](https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php)
- [https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php](https://plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php)

## Related threats

- [LiteSpeed Cache WordPress plugin authorization bypass in admin notice dismissal](https://junglewise.ai/threats/cve-2026-113501-the-litespeed-cache-wordpress-plugin-before-7-9-2-does-not)
- [LiteSpeed Cache WordPress plugin stored XSS in comment rewriting](https://junglewise.ai/threats/cve-2026-113499-the-litespeed-cache-wordpress-plugin-before-7-9-2-does-not)