Kibana version 8.7.0 contains an arbitrary code execution flaw. An attacker with All privileges to the Uptime/Synthetics feature could send a request that will attempt to execute JavaScript code. This could lead to the attacker executing arbitrary commands on the host system with permissions of the Kibana process.
https://www.elastic.co/community/security/
https://discuss.elastic.co/t/kibana-8-7-1-security-updates/332330