The Visual Basic macros in Microsoft Office 2007 SP3, 2010 SP2, 2013 SP1, and 2016 export a certificate-store private key during a document-save operation, which allows attackers to obtain sensitive information via unspecified vectors, aka "Microsoft Information Disclosure Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-107