If you use an Apple Airport base station for your wireless network, be sure you have the Airport Utility app set to give you notice of updates. These are critical security updates and you want to install them as soon as they are available.
You can do this by opening Airport Utility and then Preferences. Ensure that all the boxes are checked, and that the check is set to Daily for maximum protection or Weekly otherwise.
See 9to5Mac.com for more details.