This indicates an attack attempt to exploit a Remote Code Execution vulnerability in Microsoft SharePoint.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when handling a crafted request. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted HTTP request.
Microsoft SharePoint Enterprise Server 2016
Microsoft SharePoint Foundation 2010 Service Pack 2
Microsoft SharePoint Foundation 2013 Service Pack 1
Microsoft SharePoint Server 2010 Service Pack 2
Microsoft SharePoint Server 2013 Service Pack 1
Microsoft SharePoint Server 2019
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.