Something called has hijacked my browser. How do I get rid of it?

I have used Firefox for years and I never knowingly download unknown software. Recently I have been getting this Snap.Do search screen instead of my usual browser. Does anyone know from whence it came, is it dangerous, how do I get rid of it?

Many thanks

↓ Show more ↑ Show less
  • All posts
  • Helpful Solutions
  • solution
  • owner
  • post