Apple released updates for many of its products yesterday that address serious security vulnerabilities. Failure to apply these updates leaves your computer, phone, or tablet open to hacking over the Internet.
If you are running the following operating system versions on your Mac, iPhone, or iPad, we urge you to download and install the latest updates.
MacOS (Sierra): upgrade to MacOS 10.12.3. If you haven't upgraded your MacOS to Sierra (version 10.12), then you don't need to apply this security update.