URL redirection to an untrusted site ('Open Redirect') in Kibana can lead to sending a user to an arbitrary site and server-side request forgery via a specially crafted URL.
Unrestricted upload of a file with dangerous type in Kibana can lead to arbitrary JavaScript execution in a victim’s browser (XSS) via crafted HTML and JavaScript files.
The attacker must have access to the Synthetics app AND/OR have access to write to the synthetics indices.