Old versions of Adobe Flash Player, perhaps the most widely used software in the world, contain known bugs that are being actively exploited online. If you are using any version of Flash Player, other than the latest, you should update to version 22.214.171.124 as soon as possible.
Early reports from Symantec said the bug being exploited was a new one. Turns out this is not the case. On Thursday, Adobe said
"Despite various reports that have been circulating, the Flash Player Standalone 126.96.36.199 and Linux Player 188.8.131.52 are NOT vulnerable to the exploits discussed in conjunction with the previously disclosed vulnerability Symantec posted on 5/27/08. Symantec originally believed this to be a zero-day, unpatched vulnerability, but as their latest update on their Threatcon page indicates, they have now confirmed this issue does not affect any versions of Flash Player 184.108.40.206."
You can see which version of Flash Player is being used by your Web browser at the Adobe Flash tester page. You need to check every Web browser installed on your computer.
For instructions on updating Flash Player, see Time to update the Flash Player. Here's how. If you use the portable version of Firefox, see Portable Firefox and the Flash Player for instructions on updating Flash Player.