The keyword "Mario-Kart-8-Deluxe-Update-3.0.3.NSP.rar" refers to a compressed archive typically found on third-party file-sharing sites. Users should exercise extreme caution:
The primary purpose of the 3.0.3 update was to fix a severe security flaw in the game's netcode. Specifically: Mario-Kart-8-Deluxe-Update-3.0.3.NSP.rar
The update did not introduce any changes to graphics, sound, game balance, or character performance. Compatibility and Updates The keyword "Mario-Kart-8-Deluxe-Update-3
Players must download this update to access online features. All racers in a session must be on the same software version for local wireless or LAN play. Mario-Kart-8-Deluxe-Update-3.0.3.NSP.rar
Dataminers discovered the update modified a few lines of code to fix a buffer overflow vulnerability related to LAN and local wireless multiplayer.