Outlook Web App (OWA) in Microsoft Exchange Server 2007 SP3, 2010 SP3, and 2013 SP1 and Cumulative Update 6 does not properly validate tokens in requests, which allows remote attackers to spoof the origin of e-mail messages via unspecified vectors, aka "Outlook Web App Token Spoofing Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2014/ms14-075