This makes an interesting read .. Found it up on the Security Vulnerability Research & Defense Blog
Today we released MS08-039 which addressed several XSS vulnerabilities in Microsoft Exchange’s Outlook Web Access component. While this is an update to be applied to the Exchange server, the clients who use OWA are the computers potentially at risk. We’d like to explain a little more about the vulnerability so that you can determine whether you or your organization are at risk.
OWA has two modes: OWA Light (or OWA Basic for Exchange 2003), and OWA Premium. In short, if OWA Light/Basic is used, you are vulnerable to the XSS vulnerability. You can tell whether OWA Light is used via the “Use Outlook Web Access Light” check box in OWA’s logon screen.