However, there are some important clarifications regarding the terms "Update 3.03" and "NSP RAR" that need to be addressed.
The only 100% safe way to get Update 3.0.3 is through official channels: On Hardware : Highlight the Mario Kart 8 Deluxe icon on your Home Menu, press the Software Update , and choose Via the Internet For Emulation
What's New in Update 3.0.3?
On Switch: Just hit the '+' button on your home screen and select "Software Update." It’s free, fast, and safe.