This indicates an attack attempt to exploit a Remote Code Execution Vulnerability in Microsoft Exchange Server.
The vulnerability is due insufficient sanitization when handling a malicious configuration file. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted text file.
Microsoft Exchange Server 2016 Cumulative Update 19
Microsoft Exchange Server 2019 Cumulative Update 8
Microsoft Exchange Server 2013 Cumulative Update 23
Microsoft Exchange Server 2019 Cumulative Update 7
Microsoft Exchange Server 2016 Cumulative Update 18
Microsoft Exchange Server 2010 Service Pack 3 Update Rollup 31
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.