The "NagVis" component within Checkmk is vulnerable to reflected cross-site scripting. An attacker can craft a malicious link that will execute arbitrary JavaScript in the context of the browser once clicked. The attack can be performed on both authenticated and unauthenticated users.
https://www.nagvis.org/downloads/changelog/1.9.42
https://korelogic.com/Resources/Advisories/KL-001-2025-001.txt
https://checkmk.com/werks?version=2.3.0p10