Mozilla Firefox is failing the security interests of its users

Why when I just loaded Firefox was my saved home set of preferred tabs displaced by Ask.com? This isn't why I choose to use this browser. I quit and reloaded and the same thing happened. I checked my default set of tabs and it too had been displaced by Ask. How did this happen? I am disgusted that Firefox's developers should either permit this to happen (heaven knows what kind of commercial deal is being done at the user's cost) or release software that is so insecure it can be hijacked like this. What's their answer?