In Apache Struts 2.0.0 through 2.3.33 and 2.5 through 2.5.10.1, using an unintentional expression in a Freemarker tag instead of string literals can lead to a RCE attack.
https://veriti.ai/blog/vulnerable-villain-when-hackers-get-hacked/
https://kb.netapp.com/support/s/article/ka51A000000CgttQAC/NTAP-20170911-0001
http://www.securityfocus.com/bid/100829
http://www.oracle.com/technetwork/security-advisory/alert-cve-2017-9805-3889403.html
http://www.arubanetworks.com/assets/alert/ARUBA-PSA-2017-003.txt