You can learn more about these updates through this link/report from PC World. Noting that many of these patches are still fixing Internet Explorer vulnerabilities which affected Windows XP.
I suspect this will be an ongoing thing for the next few Tuesdays and quite possibly throughout the Summer. At least until Windows XP (finally) dies off naturally.
If you have Windows 8 or 8.1 and have yet to update to the 8.1 update be sure you do soon as Microsoft has extended this as well.