Just checked my version and it says v3.4.3 and no newer versions are available. That's odd. I am not in the U.S. so maybe hikvision released different versions in different locations.
[h=4]What's New in Version 4.2.1[/h]1. Fixed the issue of displaying only in English in iOS9. 2. Fixed security flaw caused by external malware in iOS V4.2.0. Please install or upgrade iVMS-4500 V4.2.1 for more secure service.