Flash has one big problem: No automatic updates.
Firefox checks for updates of itself and all installed add-ons. But plugins are ignored. This can lead to some troubles.
The Random Password Generator had over 3000 visits the last few days. I checked the Google Analytics statistics and only 13.85% of the visitors had a current version of Flash. Important bugfixes aren't installed on a lot of computers!
Check your Flash version!
At the time of this post, the current version is 9.0.124.0.