It feels like a satire of Silicon Valley. An engineer builds an app that does nothing but say “Yo.” The app brings in more than $1 million in angel funding. And then the app is hacked. If a comedian were going to make fun of the Web 2.0 boom, this is exactly the story they would tell.

But hold onto your chair: It’s all real.

San Francisco-based engineer Or Arbel launched the “Yo” app on April Fools’ Day this year, and even he thought it was a joke. The app allows users to send a “yo” to other users on the site. The written message “yo” appears on a user’s phone and an audible “yo” also accompanies the greeting. That’s it.

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And the app blew up. Yo, which is currently only available for iPhone usage, has received outrageously rave reviews. As of 10:40 am ET on Friday, Yo was the sixth most popular free app available for download in the Apple app store. That’s ahead of Instagram, YouTube and Facebook.

The allure, according to the Apple store description, is that the “Yo” greeting is entirely dependent on context. Think about a hug: Your mom hugs you. Your friends hug you. But when that special someone hugs you, it’s different. And when that special someone hugs you for the first time, late at night, when you are alone, then it’s really different. As it is with the “yo.”  

Earlier this week, the app pulled in $1.2 million in funding from angel investors, including Moshe Hogeg, according to Crunchbase, an online database of startup funding. Hogeg is a tech entrepreneur himself and founder of Genesis Angels, a private investment company dedicated to early-stage investments.

Less than three months after launching the app as a joke, Arbel is looking to hire developers to help build out an app for Android users and back-end engineers.

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And then, as the story goes. The app was hacked. Of course it was, right?

Vine user “hako,” from the United Kingdom, posted a video of him having the “Yo” app play music instead of saying “Yo.” Next to the Vine, Hako says, “I think I broke yo.”

Also, a couple of Georgia Tech college students emailed the tech blog TechCrunch claiming to be able to get access to user’s phone numbers. “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),” the college student told TechCrunch.

Arbel admits to having had security issues and told Entrepreneur.com in an email that he is bringing in outside forces to help them nail down the issue.

“Yo is having security issues. Some of the issues has been fixed and we are still working on the others. I cannot reveal any information about the hacks to prevent misuse of this information,” said Arbel. “We brought in a specialist security team to deal with the issues, and we are taking this very seriously.”

How ironic. What was an April Fools’ joke is now being taken so very, very seriously.

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