Microsoft Exchange Server 2007 SP3, 2010 SP3, 2013 SP1, 2013 Cumulative Update 12, 2013 Cumulative Update 13, 2016 Cumulative Update 1, and 2016 Cumulative Update 2 misparses e-mail messages, which allows remote authenticated users to obtain sensitive Outlook application information by leveraging the Send As right, aka "Microsoft Exchange Information Disclosure Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-108