A spoofing vulnerability exists in Microsoft Exchange Server when Outlook Web App (OWA) fails to properly handle web requests. An attacker who successfully exploited the vulnerability could perform script or content injection attacks, and attempt to trick the user into disclosing sensitive information. An attacker could also redirect the user to a malicious website that could spoof content or the vulnerability could be used as a pivot to chain an attack with other vulnerabilities in web services.
To exploit the vulnerability, an attacker could send a specially crafted email containing a malicious link to a user. An attacker could also use a chat client to social engineer a user into clicking the malicious link. However, in both examples the user must click the malicious link.
The security update addresses the vulnerability by correcting how OWA validates web requests.