Apache Struts 2.0.0 through 2.3.15 allows remote attackers to execute arbitrary OGNL expressions via a parameter with a crafted (1) action:, (2) redirect:, or (3) redirectAction: prefix.
https://veriti.ai/blog/vulnerable-villain-when-hackers-get-hacked/
https://exchange.xforce.ibmcloud.com/vulnerabilities/90392
http://www.oracle.com/technetwork/topics/security/cpujul2015-2367936.html
http://www.oracle.com/technetwork/topics/security/cpujan2014-1972949.html
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20131023-struts2
http://struts.apache.org/release/2.3.x/docs/s2-016.html