This indicates an attack attempt to exploit an Information Disclosure Vulnerability in Microsoft Office.
A remote attacker could exploit this vulnerability by enticing an user to open a maliciously crafted Excel file. Successful exploitation would allow the attacker to disclose sensitive information that may help in further attacks.
Microsoft Excel 2010 Service Pack 2 (32-bit editions)
Microsoft Excel 2010 Service Pack 2 (64-bit editions)
Microsoft Excel 2013 RT Service Pack 1
Microsoft Excel 2013 Service Pack 1 (32-bit editions)
Microsoft Excel 2013 Service Pack 1 (64-bit editions)
Microsoft Excel 2016 (32-bit edition)
Microsoft Excel 2016 (64-bit edition)
Microsoft Office 2016 for Mac
Microsoft Office 2019
Microsoft Office 2019 for Mac
Microsoft Office 365 ProPlus
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Apply the most recent upgrade or patch from the vendor.