CVE-2026-3375

LiteSpeed Cache <= 7.7 - Unauthenticated Stored Cross-Site Scripting via QUIC.cloud CCSS/UCSS REST API Endpoints

2026-05-26 00:00
Osvaldo Noe Gonzalez Del Rio (Os)

Strategic Overview

Status
Patched in 7.8
Affected Plugin
LiteSpeed Cache
Affected Version
<= 7.7
CVSS
7.2High
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE-2026-3375
View all LiteSpeed Cache vulnerabilities

At a glance

CVE-2026-3375 is a high-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the LiteSpeed Cache WordPress plugin, affecting versions <= 7.7. It carries a CVSS score of 7.2 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 7.8; sites on affected versions should update now. Disclosed May 2026, reported by Osvaldo Noe Gonzalez Del Rio (Os).

Vulnerability Overview

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.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Reaching this weakness in LiteSpeed Cache <= 7.7 takes no account at all. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For LiteSpeed Cache the fix is 7.8: builds <= 7.7 are affected, anything from 7.8 onward is not.

Remediation

Update to version 7.8, or a newer patched version

How does WordSec protect against this?

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: LiteSpeed Cache 7.8 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Login Security
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-3375https://www.wordfence.com/threat-intel/vulnerabilities/id/40fa29f5-525a-4986-91f9-0210a7594e46https://nvd.nist.gov/vuln/detail/CVE-2026-3375

Related records

Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C