Update 10/16/18: Sony says that it’s now rolled out a fix for the malicious message exploit.
Over the weekend, PlayStation 4 users began reporting their consoles were being rendered inoperable upon opening certain PSN messages. Sony has since acknowledged the exploit and told IGN it’s “planning a system software update to resolve this problem.”
Source: IGN.com Update: Sony Says It's Fixed Malicious PS4 Message Exploit