dbcve.org
Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-3375

HIGH · 7.2 CVSS v3.1 Published 2026-05-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
81/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The LiteSpeed Cache WordPress plugin versions up to 7.7 contain stored XSS vulnerabilities in the /wp-json/litespeed/v1/notify_ccss and /wp-json/litespeed/v1/notify_ucss REST API endpoints. These endpoints accept CSS content from QUIC.cloud callback notifications and store it to disk without sanitization, then render it inline on frontend pages without output escaping. The IP-based access control protecting these endpoints can be bypassed when WordPress is deployed behind reverse proxies, load balancers, or CDNs with certain configurations, allowing unauthenticated attackers to inject arbitrary JavaScript.

MitigationUpgrade LiteSpeed Cache plugin to version 7.8 or later. Additionally, review and properly configure reverse proxy headers (X-Forwarded-For, X-Real-IP) to ensure IP-based access controls cannot be bypassed.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check LiteSpeed Cache plugin version
    In WordPress admin, go to Plugins > Installed Plugins > LiteSpeed Cache and view the version number. Alternatively, check the plugin header in wp-content/plugins/litespeed-cache/litespeed-cache.php or read the version from the plugin's main file.
    Affected if The installed version is 7.7 or lower (any version up to and including 7.7 is affected).
  2. Verify the vulnerable REST API endpoints exist
    Attempt to access the endpoints /wp-json/litespeed/v1/notify_ccss and /wp-json/litespeed/v1/notify_ucss via curl or browser. Check if the endpoints return a valid JSON response rather than a 404.
    Affected if The endpoints are accessible and respond (this indicates the plugin version has these endpoints).
  3. Determine if the site is behind a reverse proxy, load balancer, or CDN
    Check the server configuration and HTTP headers. Look for presence of X-Forwarded-For, X-Real-IP, or Cloudflare/Cloudfront/Akamai headers in incoming requests. Review proxy configuration files (nginx.conf, apache config, or load balancer settings).
    Affected if The WordPress site is behind a reverse proxy, load balancer, or CDN without proper trusted proxy configuration, which allows IP-based access controls to be bypassed.
  4. Confirm QUIC.cloud CSS optimization features are enabled
    In WordPress admin, go to LiteSpeed Cache > Page Optimization > CSS Optimize and check if Critical CSS (CCSS) or Unique CSS (UCSS) features are turned on. These are required for the vulnerable code paths to execute.
    Affected if CCSS or UCSS optimization is enabled, meaning the plugin will call the vulnerable notify_ccss/notify_ucss endpoints.

You are affected if LiteSpeed Cache version is 7.7 or below, the QUIC.cloud CSS optimization features (CCSS/UCSS) are enabled, and the vulnerable REST endpoints are accessible, especially when the site sits behind a reverse proxy without proper IP header validation.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade LiteSpeed Cache plugin to version 7.8 or later. Additionally, review and properly configure reverse proxy headers (X-Forwarded-For, X-Real-IP) to ensure IP-based access controls cannot be bypassed.

Recommended fix Moderate confidence

Version 7.8 or later of LiteSpeed Cache plugin for WordPress

  1. 1. Log in to the WordPress admin dashboard
  2. 2. Navigate to Plugins > Installed Plugins
  3. 3. Find LiteSpeed Cache in the plugin list
  4. 4. Check the current installed version to confirm it is 7.7 or below
  5. 5. If an update is available, click 'Update Now' to upgrade to the latest version (7.8 or later)
  6. 6. Alternatively, upload the latest version of the LiteSpeed Cache plugin from wordpress.org/plugins/litespeed-cache/
  7. 7. After updating, verify the site still functions correctly, particularly pages that should have CCSS/UCSS optimization

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-3375 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data