Microsoft released some out-of-band patches a few days ago. From your perspective as an individual computer user, they're not critical, but they are important, according to Microsoft's official terminology. From the perspective of being a responsible Netizen, you should do your bit asap. This patching only takes a few minutes and doesn't even require a reboot, so why not do it now?
Run Windows Update or Microsoft Update, depending on your version of Windows, or just visit update.microsoft.com, using Internet Explorer.
[Added] Thanks, Jack, for catching the typo.