While I was visiting a page on a usual website with the built-in browser of the Android Facebook app, a pop-up just... poped-up, saying dumb stuff about my cellphone being full of viruses, etc. (Quite similar to "Virus Found" Web Browser Pop-up) Not wanting to click on anything, I just frenetically tapped the "back" button of my Android Cellphone, which prompted the pop-up to come back until eventually Google Play Store opened and offered me to install "https ://play .google. com/store/apps/details?id=com.duapps.cleaner"
Tapping the home button of my cellphone, then using the app switcher to close Facebook, everything seems to be fine again.
My question is: Is there some way to prevent this from happening again? I mean, I was visiting a (I think) perfectly legit website which I visited many time before. Also, this is the first time I see this on a phone's browser (maybe I was just lucky until now)