This indicates an attack attempt against an Security Bypass vulnerability in Microsoft Office Outlook.
The vulnerability is caused by an error when the vulnerable software handles a malicious attachment. An attacker can exploit this by sending an email with a malicious attachment to an unsuspecting user, bypassing security features when loading the document.
Microsoft Outlook 2007 Service Pack 3
Microsoft Outlook 2010 Service Pack 2 (32-bit editions)
Microsoft Outlook 2010 Service Pack 2 (64-bit editions)
Microsoft Outlook 2016 (32-bit edition)
Microsoft Outlook 2016 (64-bit edition)
Microsoft Outlook 2013 Service Pack 1 (32-bit editions)
Microsoft Outlook 2013 Service Pack 1 (64-bit editions)
Security Bypass: Remote attackers can bypass security features of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.