A stored, DOM based, cross-site scripting (XSS) flaw was found in Prometheus before version 2.7.1. An attacker could exploit this by convincing an authenticated user to visit a crafted URL on a Prometheus server, allowing for the execution and persistent storage of arbitrary scripts.
https://github.com/prometheus/prometheus/pull/5163
https://github.com/prometheus/prometheus/commit/62e591f9
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-3826