Apache Struts 2.0.0 through 2.3.15.1 enables Dynamic Method Invocation by default, which has unknown impact and attack vectors.
http://archives.neohapsis.com/archives/bugtraq/2013-09/0107.html
http://struts.apache.org/release/2.3.x/docs/s2-019.html
http://www.oracle.com/technetwork/topics/security/cpujan2014-1972949.html