Firefox, Thunderbird and SeaMonkey have had a couple of major flaws fixed. The new version for FireFerret is 188.8.131.52 and it is available now.
Automatic update notification is delivering it to users, but if you don't have that turned on, you need to upgrade now. Exploit code for one of the flaws is now confirmed to be on some compromised web sites. As far as I know; all extensions work with the new version, except the Java console, which will be fixed very soon.