CVE-2026-71285
Received Received - Intake

XSS in Uptime Kuma Matomo Analytics Integration

Publication date: 2026-08-05

Last updated on: 2026-08-05

Assigner: 309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c

Description
Uptime Kuma's Matomo analytics integration (server/analytics/matomo-analytics.js) injects the admin-configurable Matomo `siteId` value as a bare, unquoted JavaScript expression inside a <script> block rendered on every public status page: `_paq.push(['setSiteId', ${escapedSiteIdHTMLAttribute}]);`. The escaping pipeline used (jsesc with isScriptContext:true, then html-escaper.escape()) does not escape the characters `]`, `)`, `;`, `(`, which are sufficient to break out of the array/push expression context. A siteId value such as `1]);alert(document.cookie)//`, once saved by an editor/admin, executes arbitrary JavaScript for every unauthenticated visitor of the public /status/<slug> page, enabling session-cookie theft and full page takeover.

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Meta Information

Published
2026-08-05
Last Modified
2026-08-05
Generated
2026-08-05
AI Q&A
2026-08-05
EPSS Evaluated
N/A
NVD
CVE-2026-71285
EUVD
EUVD-2026-53370

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
matomo matomo *
louislam uptime_kuma *

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

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Executive Summary

Uptime Kuma's Matomo analytics integration injects an admin-configurable Matomo siteId value into a JavaScript expression on public status pages without proper escaping. This allows an attacker to craft a siteId that breaks out of the intended context and executes arbitrary JavaScript code for every unauthenticated visitor.

Detection Guidance

Check Uptime Kuma's public status pages for unexpected JavaScript execution or unusual Matomo siteId values in the page source. Inspect the rendered HTML for unquoted or improperly escaped siteId values in the analytics script block.

Impact Analysis

An attacker could steal session cookies or take over the entire page for visitors of public status pages. This requires the attacker to have admin privileges to set the malicious siteId, but once set, all unauthenticated visitors are affected.

Compliance Impact

This vulnerability could lead to unauthorized access to user data, violating GDPR's data protection principles and HIPAA's security requirements for protected health information. It may result in data breaches and non-compliance penalties.

Mitigation Strategies

Update Uptime Kuma to the latest patched version. If an update is unavailable, disable the Matomo analytics integration in the admin panel. Review and sanitize any existing siteId values to remove special characters.

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