Update Windows Right Now
Microsoft normally restricts its Windows updates to a monthly Patch Tuesday. So when the company pushes a critical update on a Monday, it’s a good sign that you need to update now!
The security update applies to all versions of Windows since Vista, and fixes a hole in the security: thanks to a bug in the way Windows handles custom fonts, a hacker could use a custom font on a webpage or document to remotely execute code on your computer. So visit one untrusted website with a goofy font, and a hacker could run code on your machine. Microsoft labelled this bug as Critical.
The fix is available now through Windows Update, and does require a restart.