Are you rooted? If not just clear your browser cache..(just to be sure hope u did total factory reset.
If you are rooted install any system level adsense app like adaway then try scan for the misbehaving app. If it wont show worry not, adaway will kill the advert string before it launches.
Lastly... Always be conscious of the apps permissions you install esp "free paid stuff" from unapproved sources...