I doubt that this would affect any up to date firmware. I'd hazard a guess that most customers that have CCTV installed by others, don't keep their systems firmware up to date and wouldn't contact the installer again unless they experienced an obvious issue such as camera or recorder failure. End users who have installed their own systems (and frequent the forums here and elsewhere) are perhaps a little more aware/tech savvy. They are more likely keep their systems up to date.
There will be a vast amount of systems still out there that still have Hikvision cameras pre 5.2 firmware that used 12345 for the admin password (prior to that firmware, plug and play did not copy the NVR admin password to the cameras - if you wanted a stronger password, the cameras had to be added manually). I guess the t**t who is responsible is just finding those cameras, logging in and adding that message using the text overlay field in the camera.