This not only adds two new cups and eight more courses but also the returning character Birdo and the new track Yoshi's Island. Apart from this, Version 2.3.0 comes with a bunch of general improvements and also resolves a number of issues. Here are the full patch notes, courtesy of Nintendo's support page:
Ver. 2.3.0 (Released March 8, 2023)
Support for DLC
- Now supports paid DLC: Mario Kart 8 Deluxe – Booster Course Pass, Wave 4 (two cups, eight courses, and one character, Birdo).
- Improved the performance of some characters and vehicle customizations.
- Made it so that the player can see the rear view mirror when spinning, crashing, or changed into Bullet Bill.
- Made it so, if the player uses a Super Star or Boo at the same time that they are hit by Lightning, their kart will not crash or become small.
- Made it so, when jumping from a Whomp in Tour Berlin Byways, karts can leap over the fence.
- Added Golden Mushroom to Custom Items in Renegade Roundup.
- Added “Booster Course Pass” button to main menu. If a player does not have the Booster Course Pass, a link to the Nintendo eShop will be displayed.
- Fixed an issue where, when the player’s kart became small after being hit by lightning, it would slip into the ground.
- Fixed an issue where, when the player’s kart ran into a wall, they would be carried over by Lakitu even though they had not left the course.
- Fixed an issue where the player character would not be able to hit an opponent with a red shell when that opponent was jumping on a half-pipe.
- Fixed an issue where the player character could not drift after jumping and landing in a half pipe.
- Fixed an issue so that the player can use another item other than Boo right after using Boo.
- Fixed an issue where the player could not throw a Boomerang after catching it and it entered the second item slot.
- Fixed an issue where, when a player character hit the Blooper in an opponent’s Crazy 8, they would have ink squirted on them even though they are using the Super Star.
- Fixed an issue where, when the player stops looking at the rear view mirror, the ink would disappear momentarily even though they had Blooper ink on them.
- Fixed an issue where, when player is hit with a red shell at the same time as changing into Bullet Bill, they would go off the course.
- Fixed an issue where, at the escalator in Wii Coconut Mall, there would be a communication error when a character could not move forward.
- Fixed an issue when changed into Bullet Bill in Dry Dry Desert, where the character would slip into the ground.
- Fixed an issue where the character would get stuck on the bridge posts right before and after the starting line in Tour London Loop.
- Fixed an issue where, on wavy floors in 3DS Rainbow Road, the character could be pushed way off the course.
Nintendo still has a bunch of other Waves it will be releasing in the future. More classic characters will also be added.