Malicious message crashes aren't just for smartphones, it seems. Numerous PS4 owners have reported receiving PSN messages where an unrecognized character effectively bricks their consoles, making them crash and leaving them unable to start properly. And deleting any rogue messages (typically by leaving the conversation in the PS Messages mobile app) isn't enough by itself -- you have to either rebuild the database in Safe Mode or factory reset the system.
You can eliminate the chance of a hostile message by going into your settings (either in the console or the PS Messages app), visiting account management, and then changing your privacy settings so that messages are either limited to friends or switched off.
We've asked Sony for comment. The company can likely address this with a software update, and it's relatively easy to protect yourself in the meantime. However, there's little doubt that the consequences are serious. Most phone-oriented bugs are troublesome, but won't necessarily prevent you from using your other apps on your device. Here, a prankster is rendering your PS4 effectively inoperable until you walk through some painstaking troubleshooting steps.