If you use the Greasemonkey extension to Mozilla Firefox (both of which I highly recommend), you should update to the latest version immediately. A serious security hole has been found which lets web sites send any file on your computer to anybody. This applies to all platforms which can run Firefox. The latest version doesn't have this problem, but a few Greasemonkey scripts may break. I haven't had trouble with the upgrade, but you might.
UPGRADE
Serious security hole in Greasemonkey
Moderator: Thanas