Download the Microsoft Security Scanner to check if you have any malware infecting any files. If the test returns positive (There are viruses), you will need to take your computer into an IT professional to have your files backed up and then have the hard drive wiped completely. Contact your bank/credit union/building society if you suspect your credit card details have been compromised.

I know how to fix the problem. I'm an IT consultant.

I only wanted to highlight the issue to Mozilla.

Oh... Firefox staff don't regularly participate in these forums, then encourage people to send feedback here http://input.mozilla.com/en-US/feedback

Thanks Dav.

You're welcome. If this solved your problem please mark this as a solution to archive this post