In Grafana 2.x through 6.x before 6.3.4, parts of the HTTP API allow unauthenticated use. This makes it possible to run a denial of service attack against the server running Grafana.
https://security.netapp.com/advisory/ntap-20191004-0004/
https://grafana.com/blog/2019/08/29/grafana-5.4.5-and-6.3.4-released-with-important-security-fix/
https://github.com/grafana/grafana/releases
https://community.grafana.com/t/release-notes-v6-3-x/19202
https://community.grafana.com/t/grafana-5-4-5-and-6-3-4-security-update/20569
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00009.html
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00083.html
http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00060.html