This indicates an attack attempt to exploit a Remote Code Execution vulnerability in Apache Struts.
The vulnerability is due to insufficient validation of user supplied inputs in the application. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted request.
Apache Software Foundation Struts 2.3.20 to 220.127.116.11
System Compromise: Remote attackers can gain control of vulnerable systems.
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