As reported by several users on Reddit, there's a message being sent around that basically bricks the PlayStation 4, forcing players to reset the console to factory settings. It seems this is a regular message, but something in it will exploit the firmware's code and block the console, rendering it useless.
Users also report that even deleting the message via the PSN app won't work, and some even claim you don't have to read it, as receiving it might break your console anyway.
Sony has yet to acknowledge this glitch or offer an official response, but if you'd rather play it safe, it seems setting your messages to private will prevent you from receiving the message. To set this up you need to do the following:
Settings > Account Management > Privacy Settings > Personal Info > Messaging. Set Messages to Friends or No One.
We will keep you updated as the situation develops.