Kibana versions before 5.6.15 and 6.6.1 contain an arbitrary code execution flaw in the Timelion visualizer. An attacker with access to the Timelion application could send a request that will attempt to execute javascript code. This could possibly lead to an attacker executing arbitrary commands with permissions of the Kibana process on the host system.
https://www.cisa.gov/news-events/cybersecurity-advisories/aa24-207a
https://www.elastic.co/community/security
https://discuss.elastic.co/t/elastic-stack-6-6-1-and-5-6-15-security-update/169077
https://access.redhat.com/errata/RHSA-2019:2860