The remote host is running a version of the Outlook Web Access which contains cross site scripting flaws. This vulnerability could allow an attacker to convince a user to run a malicious script. If this malicious script is run, it would execute in the security context of the user. Attempts to exploit this vulnerability require user interaction. This vulnerability could allow an attacker access to any data on the Outlook Web Access server that was accessible to the individual user. It may also be possible to exploit the vulnerability to manipulate Web browser caches and intermediate proxy server caches, and put spoofed content in those caches.

http://www.microsoft.com/technet/security/bulletin/ms04-026.mspx