One MS Security Bulletin issued today.
This update resolves a newly-discovered, privately reported vulnerability. A cross-site scripting and spoofing vulnerability exists in Outlook Web Access for Exchange Server 5.5 that could allow an attacker to convince a user to run a malicious script.
An attacker who successfully exploited the vulnerability could manipulate Web browser caches and intermediate proxy server caches, and put spoofed content in those caches. They may also be able to exploit the vulnerability to perform cross-site scripting attacks.