Microsoft releases out of band update for Visio and Internet Explorer on 2009-07-28 1pm US/Eastern

"While we can’t go into specifics about the issue prior to release, we
can say that the Visual Studio bulletin will address an issue that can
affect certain types of applications. The Internet Explorer bulletin
will provide defense-in-depth changes to Internet Explorer to help
provide additional protections for the issues addressed by the Visual
Studio bulletin. The Internet Explorer update will also address
vulnerabilities rated as Critical that are unrelated to the Visual
Studio bulletin that were privately and responsibly reported."

Microsoft is holding some conference calls 3 hours after the update is
released to go over what the update entails.

It is difficult to render advise on whether to install this patch ASAP
or wait to figure out what it fixes first. The out of cycle release of
the patch and secrecy about its contents may suggest immediate
deployment of the patch.