A group of hackers called Wii U Hax has claimed to have discovered an exploit in the Wii U that will enable homebrew apps. According to the team, the exploit can be found in the Wii Mode of the system, which can then be used to access the Wii U hardware. The team says the exploit can’t be patched by Nintendo through updates, as many exploits were in the era of the original Wii.
There’s currently no code being released at the moment and this isn’t unlike the same claims made by the fail0verfl0w group a few months ago.