Adobe released version 10 of its Flash player; it includes a variety of security improvements. One of these is specifically designed to prevent clipboard hijacking, such as the link some users saw a couple of weeks ago. 

Version 10 also includes other security fixes; Adobe sees this as a critical update:

Adobe recommends all users of Adobe Flash Player and earlier versions upgrade to the newest version by downloading it from the Player Download Center, or by using the auto-update mechanism within the product when prompted. Adobe will be providing an update to Flash Player 9 for customers who cannot upgrade to Flash Player 10 in early November. This Security Bulletin will be updated once the Flash Player 9 update is available.

This means webmasters better have a look at the list of changes, because some applications might be incompatible with version 10:

Adobe Flash Player 10 offers a variety of new features and enhancements as well as some changes to the previous behavior of Flash Player. Some of these changes may require existing content to be updated to comply with stricter security rules.