---
id: "CVE-2026-16889"
kind: "vulnerability"
aliases: ["CVE-2026-16889"]
title: "openEQUELLA: pre-login notice image upload serves HTML as stored XSS"
severity: "medium"
cvss: 4.8
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["openequella", "package", "self-hosted"]
not_affected_if: ["edit-system-settings-restricted", "version-2026.1-or-later"]
published_at: "2026-10-29T02:16:51+00:00"
first_seen_at: "2026-10-29T02:36:47+00:00"
updated_at: "2026-10-29T02:38:05+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-16889", "first_seen_at": "2026-10-29T02:36:47+00:00"}]
---

# openEQUELLA: pre-login notice image upload serves HTML as stored XSS

openEQUELLA's pre-login notice image upload endpoint does not check file types and serves uploads with a Content-Type taken from the filename. An uploaded HTML file is then rendered from the openEQUELLA origin, so an attacker can run scripts in other users' sessions.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Confirm the installed openEQUELLA version is earlier than `2026.1`.
- Check which roles hold `EDIT_SYSTEM_SETTINGS`, and whether the guest user or everyone has it.

## Fix

- Upgrade openEQUELLA to `2026.1` or later.
- Until upgraded, remove `EDIT_SYSTEM_SETTINGS` from the guest user and everyone roles.

## Timeline

- 2026-10-29T02:36:47+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-16889

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_