If you have an Apple device (iPhone, iPad, Watch, AppleTV, Mac), please update it as soon as possible. This, as with any other security updates, I stress, must be done as soon as you can.
For iPhone/iPad, go to “Settings → General → Software Update”, and choose to install. For WatchOS, go to “Settings → General → Software Update”, and follow the instructions to upgrade. Finally, for macOS go to “System Settings → General → Software Update” (on older versions is a bit different, but you get the general idea).