What’s Vulnerable › Vulnerabilities

CVE-2026-16889: Stored XSS via Pre-Login Notice Image Upload Serves Attacker HTML from Application Origin

• Severity: medium (CVSS 4.8 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-29 · updated 2026-10-29
• Weakness: CWE-434

Description

In openEQUELLA before 2026.1, the pre-login notice image upload endpoint (PUT /api/preloginnotice/image/{name}) does not validate the type of uploaded files and serves them with a Content-Type derived from the supplied filename. A user holding the EDIT_SYSTEM_SETTINGS permission can upload an HTML file that is then served as text/html from the openEQUELLA origin, resulting in stored cross-site scripting. Unauthenticated exploitation is possible where EDIT_SYSTEM_SETTINGS has been granted to the guest user or everyone.

Affected products

• Apereo Foundation openEQUELLA: from 2019.1 before 2026.1 — fixed in 2026.1

How to fix

Upgrade to a fixed version: Apereo Foundation openEQUELLA 2026.1. Check the vendor advisory for mitigations.

References

• https://github.com/openequella/openEQUELLA/security/advisories/GHSA-q2xv-rffq-mj5w
• https://openequella.github.io/guides/

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