Microsoft Excel 2003 SP3, 2007 SP3, and 2010 SP1 and SP2; Excel Viewer; and Microsoft Office Compatibility Pack SP3 allow remote attackers to read arbitrary files via an XML document containing an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue, aka "XML External Entities Resolution Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A18686
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2013/ms13-073