Posting to pass on info to parents of teens....
YUBO (formerly known as yellow) is an app for teenagers to meet local teens, to chat to and make new friends. It's available from age 13, which means that parental controls will not block the use of it.
It's basically Tinder for teens, full of people asking for and sending 'nudes' I have reported it to my teenagers schools safeguarding officer, as it seems that most of her friends are also using the app.