You might not have to dread receiving a message on your PS4. Sony's Twitter-based PlayStation UK support has told customers that the company has "fixed the issue" that let malicious PSN messages crash consoles. While the team didn't explain what had been done to address the problem (we've asked Sony for more details), there's no firmware update involved. This suggests that any fix would have been on Sony's end, such as blocking messages with the unrecognized characters.
The company also reiterated that the messages 'only' triggered a crash loop, and that you could recover the PS4 by first deleting the rogue messages in the PS Messages app and then choosing to rebuild the database from the system's Safe Mode menu.
Provided there is a solution in place, you'll still need to be on guard if you received a message and haven't fired up your console since. And regardless of whether or not you're affected, it's as good a time as any to review your message privacy settings. If you don't want to risk future problems or just don't see a need to receive messages from strangers, you might as well limit messages to "friends only."
We've since fixed the issue, and it wasn't bricking consoles, just sending them into a crash loop that can be quickly fixed in under 5 minutes. Delete the message on the PS mobile app, go into Safe Mode, use Option 5, console back to normal. ^DB— Ask PlayStation UK (@AskPS_UK) October 15, 2018