Yo, the free app that only lets you send yo in messages to friends, is currently experiencing security issues. After rising rapidly in popularity and entering the US App Store’s Top 10 list, TechCrunch reports that Yo has been hacked by three college students. The hack allegedly reveals any Yo users’ phone number, and enables message spoofing with the ability to send any text-based push notification to devices. Or Arbel, founder of Yo, has confirmed the security problems in a statement to TechCrunch, and notes that the company has addressed some of them.