Did anyone visit that site, Spicy? Is it possible that another family member, or a friend, used your pc to access that site? If you are quite certain that the answer to those questions is 'no', then I think you should look at other postings - and should certainly complain to Trading Standards and elsewhere.
As I understand it, the websites using MBS software now have warnings prominently displayed. I never go near such sites, so am loath to check this out personally. Can others comment on this?