Several days ago, word was going around that an exploit was allowing bad actors to send malicious messages through the PlayStation Network, which upon receipt would brick PlayStation 4 consoles. This would happen regardless of whether or not the victim of the practice actually opened the message. Sony has fixed the issue and also clarified what was actually happening. Luckily, no consoles were actually bricked.
The issue has been fixed via a firmware update, so the bug should no longer be a threat. If you changed the security settings on your PSN account, feel free to open them back up if you want. Perhaps more importantly are instructions provided by Sony that can fix the issue for any affected console owners.
PlayStation support noted that consoles weren’t bricked, they were stuck in crash loops. All you need to do to fix it is get the PlayStation mobile app, and delete the offending message. From there, boot the PS4 into safe mode and pick the fifth option. After that, the console should be fine.