Kibana versions before 6.4.3 and 5.6.13 contain an arbitrary file inclusion flaw in the Console plugin. An attacker with access to the Kibana Console API 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.elastic.co/community/security
https://discuss.elastic.co/t/elastic-stack-6-4-3-and-5-6-13-security-update/155594