Yo app: what is it and why is it popular?

The creators of the Yo app, which allows users to do nothing but say "Yo" to one another, are still trying to fix a security flaw with the program.

Yo has been labelled "stupid" by US TV host Stephen Colbert who lampooned the simple app saying "there's a new app that has expanded the possibilities for communication by drastically reducing them".

But interest in Yo has spread at viral speeds and the team behind the app has managed to raise over $1 million in venture capital funding.

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On Friday, app developer Or Arbel announced that Yo was "having security issues", but said members of his team were working on getting them fixed as quickly as possible. As of this morning, neither the Android nor iOS versions of the app have received updates.

What does the Yo app do?

Yo bills itself as the "simplest and most efficient communication tool in the world". With a single tap, users can send the word "Yo" to one another – and nothing else. The app's developers note that sending the same message using WhatsApp, Facebook or SnapChat would take 11 taps.

Yes, but what if I want to say something else?

You can't. But Yo claims that this limitation is also its inherent strength. "Wanna say 'good morning'? Just Yo. Wanna say 'Baby I'm thinking about you'? – Yo. 'I've finished my meeting, come by my office?' – Yo… The possibilities are endless" the app's developers explain on iTunes.

What do Yo users say?

Some users are raving about the app's potential with tongue-in-cheek reviews online, the Daily Mail notes. "Since downloading Yo, all my relationships have improved and I've regrown most of my hair," said one reviewer on iTunes. "Receiving a yo is fast becoming the highlight of my day," added another on the Google Play store. Many others don't see the point and have given the app a one-star review. Yo currently has a middling three-star rating on iTunes.

What is the security flaw?

A Georgia Tech student told Techcrunch that he had managed to bypass Yo’s security. “We can get any Yo user’s phone number (I actually texted the founder, and he called me back)”, the student said. "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)." Arbel later confirmed the hack.

So is Yo just pointless?

In its current incarnation Yo might not offer very much, but Forbes's Anthony Wing Kosner believes the app has huge potential. "If a 'Yo' could also contain a link, the impact would be huge" Kosner says.

He adds: "Consider the meaning of a 'yo' with a map location, with a web address, with a song or a YouTube video? The ability to shout out the immediate context is what Twitter is supposed to be for, but who wants to bother crafting 140 characters anymore?"

Kosner also believes that Yo could be the perfect app for the much-anticipated Apple smartwatch.

The first step will be to fix the app's security issues. But with Yo still riding high in the app charts, Android Headlines says that the hack may actually have helped, rather than hindered Arbel. Sometimes "bad press is good press", the site concludes.