Earlier today Microsoft released an out of band (i.e. un-scheduled) security update to resolve 1 CVE (defined) in the Microsoft OpenType Font Driver. At this time, no Known Issues are listed for this update within the revised Security Bulletin Summary page. I have installed this update on multiple Windows 8.1 64 bit and Windows 7 64 bit systems with no issues. The update does require a system restart.
Please install this update as soon as possible since it is a critical update and as mentioned in the security bulletin consistent exploitation of this vulnerability is possible. This security bulletin also lists workarounds should you not be able to apply the update at this time.