I've got my 12mm camera: 2CD2012WD-1, and it came with WAY OLD firmware 5.2 or so... (Password is 12345 !! That Old!)
Anyway, went to Hikvision-US and downloaded latest, and all older firmware versions I could find... and stared Upgrading firmware...
Got to
V5.4.5 build 170123 in 3 steps...