This exploit was fixed with the v1.1.3 Smash Bros game update released on December 15, 2015. The previously vulnerable function is now identical to the one from the updated demo mentioned above. See below regarding running old game-versions.
EUR and JPN full-game .code binaries addresses-wise are basically the same, for v1.0.4 at least. Hence, the filenames for these two regions include "gameother".
This can't be completely blocked with the main app without a system-update: even if an app-update would fix it, one could just rename/whatever the update-title directory on SD card to force the system to not use the update-title(the directory name could be restored to the original later when not using this hax). One could also do this if the currently installed update-title version is not supported, or when the latest version of the update-title isn't supported(where the currently installed version isn't supported).
The above mentioned directory is at the following SD card location: "/Nintendo 3DS/{ID0}/{ID1}/title/0004000e/{TIDHigh}". Where TIDHigh for the update-title is one of the following:
- USA: 000edf00
- EUR: 000ee000
- JPN: 000b8b00