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Vulnerability Advisory : ApostropheCMS: Stored XSS in SEO Fields Leads to Authenticated API Data Exposure in ApostropheCMS with LOW Attack Complexity

Summary

ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain a stored cross-site scripting vulnerability in SEO-related fields (SEO Title and Meta Description), where user-controlled input is rendered without proper output encoding into HTML contexts including <title> tags, <meta> attributes, and JSON-LD structured data. An attacker can inject a payload such as "></title><script>alert(1)</script> to break out of the intended HTML context and execute arbitrary JavaScript in the browser of any authenticated user who views the affected page. This can be leveraged to perform authenticated API requests, access sensitive data such as usernames, email addresses, and roles via internal APIs, and exfiltrate it to an attacker-controlled server. This issue has been fixed in version 4.29.0.

Impact Assessment

Timeline

Published

April 15, 2026

Last Modified

April 15, 2026

Related Advisories

to break out of the intended HTML context and execute arbitrary JavaScript in the browser of any authenticated user who views the affected page. This can be leveraged to perform authenticated API requests, access sensitive data such as usernames, email addresses, and roles via internal APIs, and exfiltrate it to an attacker-controlled server. This issue has been fixed in version 4.29.0.","datePublished":"2026-04-15T20:16:36.353Z","dateModified":"2026-04-15T20:16:36.353Z","author":{"@type":"Organization","name":"Deepaegis","url":"https://deepaegis?.io"},"publisher":{"@type":"Organization","name":"Deepaegis","logo":{"@type":"ImageObject","url":"https://deepaegis?.io/logo?.png"}},"mainEntityOfPage":{"@type":"WebPage","@id":"https://deepaegis?.io/vulnerability-advisories/apostrophecms-stored-xss-in-seo-fields-leads-to-authenticated-api-data-exposure-in-apostrophecms"},"keywords":"CVE-2026-35569, , apostrophecms, apostrophe"}