Adobe has released updates to Adobe Flash Player. This update addresses critical security problems. If you you have Flash Player installed on your computer (which is likely), please update it.
Looks like if you let Firefox and Google Chrome update themselves, that may be enough to update Flash Player in those browsers. Otherwise, the Adobe Flash Player page can tell you if you need an update (you may want to visit this page in each web browser you use).
For more technical information, see the Adobe security bulletin.
This bulletin also includes an update for Adobe AIR. If you think AIR is installed on your computer, here’s the Adobe AIR page.