PlayStation 4 users are reporting a messaging glitch that's causing some consoles to brick forcing owners to factory reset their PS4 systems. The exploit is used via the PS4's in-console messaging system and can be prevented by setting messages to private.
On the PS4 subreddit there are reports from players who received strange messages that once opened caused their consoles to lock up. Apparently even receiving the notification of the message can cause a forced reset.
A top post on the subreddit is warning other users to set their messages to private lest they fall victim to the bug. They explain that it happened to them and their party members during a game of Rainbow Six: Siege, and that the only party member not affected was the one who had their messages set to private.
While there's no official explanation for the bug, many in the thread are speculating that the attacks are like a text-exploit used to crash iPhones a couple years back. Those attacks took advantage of exploits in the code that processed texts.
There's no official word from Sony regarding this exploit but in the meantime you can set your messages to private by logging into your PS4, going into Account Management, then Privacy Settings, to Personal Info where you can set messages to either Friends Only or No One.