This indicates an attack attempt to exploit an Information Disclosure vulnerability in Microsoft Office.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted xls file. A remote attacker may be able to exploit this to gain information regarding process address space in the affected application, via a crafted xls file.
Microsoft Office 2007
Microsoft Office 2010
Microsoft Office 2013
Microsoft Office 2013 RT
Microsoft Office 2016
Microsoft Office Compatibility Pack Service Pack 3
Microsoft Excel Viewer
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Apply the most recent upgrade or patch from the vendor.