This indicates an attack attempt to exploit a Security Bypass vulnerability in Microsoft Office.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted xla file. A remote attacker may be able to exploit this to bypass security mechanism in the affected application, via a crafted xla file.
Microsoft Office 2010
Microsoft Office 2013
Microsoft Office 2013 RT
Microsoft Office 2016
Security Bypass: Remote attackers can bypass security features of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.