Microsoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4.5.2, 4.6, and 4.6.1 allows remote attackers to read arbitrary files via XML data containing an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue, aka ".NET Information Disclosure Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-091