The update will feature nine Microsoft Security Bulletins affecting Microsoft Windows, at least one of which is critical. One patch will change how Internet Explorer handles ActiveX controls, the results of a lawsuit, not a security problem.
Microsoft issued a "compatibility patch" in April to give developers time to adjust to the new method of handling controls, but with this patch, that compatibility bridge will go away.
Microsoft will not provide details on the security flaw until the patch is released, which should give some indication of the severity of the flaw. Some of these patches will require a server restart.