Microsoft has released an emergency patch for Internet Explorer.
You can install the patch using Windows Update, and read Microsoft's announcement here.
This patch is supposed to fixes a bug that allows you to get hacked if you visit wrong websites. Even if you don't use Internet Explorer as your primary browser, you should still go ahead and get this patch, because Internet Explorer is integrated into Windows Operating Systems in so many ways you might not even be aware of.
While he same bug does not exist in Microsoft's new "Edge" browser, if you are using Wmdows 10, you still need the patch because Windows 10 includes Internet Explorer 11 as well as Edge.