Apache Struts 2.0.0 to 2.5.20 forced double OGNL evaluation, when evaluated on raw user input in tag attributes, may lead to remote code execution.
packetstormsecurity.com/files/160108/Apache-Struts-2.5.20-Double-OGNL-Evaluation.html
packetstormsecurity.com/files/160721/Apache-Struts-2-Forced-Multi-OGNL-Evaluation.html
cwiki.apache.org/confluence/display/ww/s2-059
launchpad.support.sap.com/#/notes/2982840
lists.apache.org/thread.html/r1125f3044a0946d1e7e6f125a6170b58d413ebd4a95157e4608041c7%40%3Cannounce.apache.org%3E
lists.apache.org/thread.html/r90890afea72a9571d666820b2fe5942a0a5f86be406fa31da3dd0922%40%3Cannounce.apache.org%3E
www.oracle.com/security-alerts/cpuApr2021.html
www.oracle.com/security-alerts/cpujan2021.html
www.oracle.com/security-alerts/cpuoct2021.html