Microsoft has decided to update out-of-date Windows versions, such as XP, and Windows Server 2003 as a result of WannaCry and other hacks that took advantage of such systems. Windows 10 and Windows 8.1 should receive the patches automatically, assuming they are set to receive automatically.
These security updates are being made available to all customers, including those using older versions of Windows.[url]Windows 10 Tuesday Update Patches WannaCry on Win XP and Win Server 2003[/url]
Technical information about the release is available here [blogs.technet.microsoft.com
Here's more information on the update for systems other than Windows 8.1 and Windows 10 [answers.microsoft.com