Kibana versions before 6.8.11 and 7.8.1 contain a denial of service (DoS) flaw in Timelion. An attacker can construct a URL that when viewed by a Kibana user can lead to the Kibana process consuming large amounts of CPU and becoming unresponsive.
https://www.oracle.com//security-alerts/cpujul2021.html
https://www.elastic.co/community/security/
https://discuss.elastic.co/t/elastic-stack-6-8-11-and-7-8-1-security-update/242786