Sometimes visiting a site is enough to encourage an infection which is why in the year 2012 not using a proper addblocker and sometimes no script is a necessity. A lot of viruses come through adds or java and basically store themselves automatically in your temp files.
I had this a week ago while using a proper addblocker. Visited a normal legit site on the tokyo game awards and MSE gave me an infection warning, it froze though and couldn't do anything. Which is why you have something like Malwarebytes which only scans when told to and which removed the pesky pest before it could enable the lock on ability most modern viruses have. Remember if you have a lock on virus you can still enter safe mode and there you can blast it with malwarebytes and combofix