Looking it up lead me here, this website said the following:
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.
Which is good because now this means that we could execue commands and get a reverse shell.
Exploit
Open Kibana
Past one of the following payload into the Timelion visualizer