Cisco Talos warns users that they need to keep a close eye on unsecured Elasticsearch clusters. We have recently observed a spike in attacks from multiple threat actors targeting these clusters. These attackers are targeting clusters using versions 1.4.2 and lower, and are leveraging old vulnerabilities to pass scripts to search queries and drop the attacker’s payloads. These scripts are being leveraged to drop both malware and cryptocurrency miners on victim machines.

https://blog.talosintelligence.com/2019/02/cisco-talos-honeypot-analysis-reveals.html