This indicates an attack attempt to exploit a Insecure Deserialization vulnerability in Microsoft SharePoint.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when a crafted BDC model is imported. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted request to a system that has imported the BDC model.
Microsoft SharePoint Enterprise Server 2016
Microsoft SharePoint Server 2019
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.