On October 11, 2023, users accessing the Wii Menu on the Wii U console found that nearly all previously downloaded Virtual Console titles and Wii software displayed a "Update Save Data" prompt. This required users to re-download or patch their existing save files. Notably, this update was not a system firmware update, but targeted specifically at the persistent storage (NAND) of the Wii software environment.
When you insert a Wii disc and play for the first time, the console creates a basic save file (often around a few dozen blocks in Wii System Memory). An “updated” save file typically occurs in two scenarios: wii save files updated
If you see an error saying the save file was updated on a different Wii or disc version: On October 11, 2023, users accessing the Wii
Here is a summary paper/report on that topic, along with a technical breakdown of Wii save file structures. When you insert a Wii disc and play