This indicates an attack attempt to exploit an Memory Corruption vulnerability in Microsoft Office Excel.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted XLSB file. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted XLSB file.
Microsoft Excel 2010 Service Pack 2 (32-bit editions)
Microsoft Excel 2010 Service Pack 2 (64-bit editions)
Microsoft Excel 2013 Service Pack 1 (32-bit editions)
Microsoft Excel 2013 Service Pack 1 (64-bit editions)
Microsoft Excel 2013 RT Service Pack 1
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.