Yo app hacked to say things that aren't 'Yo'

Well, that didn't take long.

Yo: It used to be that simple

Yo, the fundamental rule of which is that you can only say 'Yo', has been hacked by college students, with the app being made to send various other messages and even Rick Roll users.

The Poke-like service has attracted hundreds of thousands of users in the last 48 hours, but the hack threatens to take the sheen of it now new words have entered its vocabulary.

In an email to TechCrunch, a hacker alleged: "We can get any Yo user’s phone number (I actually texted the founder, and he called me back). We can spoof Yo’s from any users, and we can spam any user with as many Yo. We could also send any Yo user a push notification with any text we want (though we decided not to do that)."

Yo has now confirmed that it is having "security issues", which it is working on and "taking very seriously".

One Instagram user posted a screengrab of them receiving the message "wow. many 1337. such bad security." through the app, while on Vine Yo was seen playing bursts of Rick Astley's Never Gonna Give You Up.

Yo founder Or Abel raised $1 million to develop the app, which is available on iOS and Android.