Apache Druid includes the ability to execute user-provided JavaScript code embedded in various types of requests. This functionality is intended for use in high-trust environments, and is disabled by default. However, in Druid 0.20.0 and earlier, it is possible for an authenticated user to send a specially-crafted request that forces Druid to run user-provided JavaScript code for that request, regardless of server configuration. This can be leveraged to execute code on the target machine with the privileges of the Druid server process.
https://www.darkreading.com/cloud-security/lucifer-botnet-heat-apache-hadoop-servers
https://www.aquasec.com/blog/lucifer-ddos-botnet-malware-is-targeting-apache-big-data-stack/
http://www.openwall.com/lists/oss-security/2021/01/29/6
http://packetstormsecurity.com/files/162345/Apache-Druid-0.20.0-Remote-Command-Execution.html