Comment 2 for bug 335084

This bug could be a result of a simple malicious javascript segment:
document.body.onload = window.open(window.location);

That said, I would've thought the popup blocking features would prevent such a script...

Still, if it is the cause of the bug then chances are it can only be "fixed" by making the popup blocking features more restrictive. Have you disabled or changed the settings for the popup blocker?

Can I assume from the fact that you have not included links to the sites you were perusing when the incident occured because you are unwilling or reluctant to do so? It might be wise for you to avoid the sites in the future, as I doubt this bug is an accident or the result of incompetent web design. It seems malicious.

By the way, you can kill all running processes of a certain name by executing the command "killall". For example, "killall firefox". This would be a faster way of killing the rogue firefox than multiple Ctrl+W calls. This would also tell firefox that something is wrong (whereas Ctrl+W doesn't) and you are closing it because it's gone wrong. This should cause a prompt asking you if you want to restore your previous session or start a new one when you re-open firefox. Restoring your previous session is, of course, the wrong course of action in this case.

One more thing:
When choosing software, one should take into consideration all available software which suits the purpose for which you will be using it. The various browsers that exist all have their merits and drawbacks, and given the opportunity to review these you may find another browser does suit your needs better than Firefox. However, with the greatest of respect, there is no need to tell us that you are changing browser. Since you have mentioned it, however, I would urge caution where making rash decisions because of a bug. To find a software package which performs exactly as expected, 100% of the time is to find the Holy Grail of package maintenance.