Where you can either register to automatically receive Security Bulletins, or select the product and Service Pack you are running to view the security bulletins that are available for your system – or both. In any case, this is a passive service that will help you see what you should have, not what you already have.
(Screenshot of the selection menu and some of the latest bulletins)
Visit this URL for the Microsoft Security Bulleting page
Note: This is not a scanning tool and it cannot be used to determine the missing patches that are on your system or network. Also, you should know that it cannot be used to scan your own machine, not to mention remote ones.
The Security Bulletin page is mostly effective in knowledge gathering and separate downloading of any security patch in Microsoft’s history.
I’ve gathered the most recent security bulletins under this page: Latest MS Security Bulletins