Last month Adobe released version 10 of their free Flash Player plugin for web browsers. If you've installed version 10, then you're done. You are not missing any patches and can stop reading now.
If you're not sure which version of Flash is installed, Adobe has a tester page. Windows users that have installed another browser, need to run this test in both Internet Explorer and the other web browser(s).
Anyone still running version 9 of the Flash Player needs to be running the latest edition, 9,0,151,0, which was released just a few days ago. It fixed a slew of bugs.
If you have an older edition of version 9, then you have a choice.
To install version 10 see my October 18th posting Seven steps to update the Adobe Flash Player on Windows. But, version 10 seems like a big change, and for defensive computing, it's often best to avoid the bleeding edge.
The problem with updating to version 9,0,151,0 is finding it. Adobe recommends using version 10 and that's the only available version at the Flash Player Download page. But, version 9,0,151,0 is available from Adobe at Flash Player 9 for Unsupported Operating Systems. There are links for Windows, Macs and Linux.
Although not always necessary, I suggest doing a full un-install of the Flash player before installing a new version. For more on this see How to uninstall the Adobe Flash Player plug-in and ActiveX control. For documentation on the fixes to the latest edition of version 9 see Flash Player update available to address security vulnerabilities.