Improper Access Control
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."
CWE-284 - Improper Access Control
Listed 5th in the 'OWASP Top Ten', improper (or broken) access control attacks are a fundamental type of vulnerability. This includes a broad range of design flaws that enable users to act outside of their intended permissions. They can use these privileges to gain access to restricted files and functionality such as accessing restricted information, falsifying records, destroying data, or executing commands.