It was discovered that Kibana’s JIRA connector & IBM Resilient connector could be used to return HTTP response data on internal hosts, which may be intentionally hidden from public view. Using this vulnerability, a malicious user with the ability to create connectors, could utilize these connectors to view limited HTTP response data on hosts accessible to the cluster.
https://discuss.elastic.co/t/kibana-7-15-2-security-update/288923