This indicates an attack attempt against a remote Code Execution vulnerability in Microsoft Office.
The vulnerability is caused by an error when the vulnerable software handles a specially crafted RTF file. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted RTF file.
Microsoft Office 2007
Microsoft Office 2010
Microsoft Office 2013
Microsoft Office 2013 RT
Microsoft Office 2016
Microsoft Office for Mac 2011
Microsoft Office 2016 for Mac
Microsoft Word Viewer
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.