The REST Plugin in Apache Struts 2.1.1 through 2.3.x before 2.3.34 and 2.5.x before 2.5.13 uses an XStreamHandler with an instance of XStream for deserialization without any type of filtering, which can lead to remote code execution when deserializing XML payloads.
View the template here CVE-2017-9805.yaml
References:
https://struts.apache.org/docs/s2-052.html