This indicates an attack attempt to exploit an Elevation Of Privilege Vulnerability in Microsoft Exchange Server.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted XML file. A remote attacker may be able to exploit this to leverage their privileges on vulnerable systems.
Microsoft Exchange Server 2010 Service Pack 3
Microsoft Exchange Server 2013 Service Pack 3
Microsoft Exchange Server 2016 Service Pack 3
Microsoft Exchange Server 2019 Service Pack 3
Privilege Escalation: Remote attackers can leverage their privileges on vulnerable systems.
Apply the most recent upgrade or patch from the vendor.