Haven't got what you describe, but last week when browsing the forum on my phone it kept trying to force me to download the William Hill app. Super annoying.
Edit: Above post beat me too it. I type to slow on this phone.
It's a bit of Adware called "Media player". Virus prog doesn't pick it up as a problem but it's damned annoying. Initially it only showed itself on this forum webpage but soon starts popping up on every page!
Uninstalled and now clear but as I didn't choose to install in the first place I guess it could be back again in future.
I haven't seen anything on my side, I have noticed lately when surfing some sites on my android phone, you get these popups saying virus detected etc. I just cancel and continue, but is annoying.