Yo, the app that lets you send only "Yo!" to your friends, has been hacked.

Quartz reports that developers discovered a security flaw that reveals users' phone numbers.

The vulnerability involved the way the app sends messages to its users, taking advantage of an infrastructure issue that leaves the database of users' phone numbers open to anyone capable of sending a request for the information.

Developers concerned over just how easy it was to access users' information took to Twitter to discuss the issue, even creating the hashtag #YoBeenHacked.

Developers used the app's vulnerability to send out an announcement and warning of the security flaws.

Yo creator Or Arbel told TechCrunch that the app did have security issues, saying the team was "taking this very seriously."

For those wanting to take precaution, deleting the app until a full fix and update has been added might not be a bad idea.

You can read our full interview with Yo's creator here.