Cliff notes. Some people are getting messages through psn. And just having the message sent to you will make your PS4 turn off. And you can't turn it back on as long as the message is on there. If it happens you can go into your psn messages on a different device and delete the message there, and then you have to rebuild the ps4 data base. So it's not the end of the world but it sure would fukk your day up.
You can avoid getting it all together by going to settings>privacy settings> message settings. And set your shyt to no one or only friend being able to message you. Everyone should probably do that until the shyt gets figured out.