3DS:Soundhax

Soundhax is a homebrew entrypoint for Nintendo 3DS consoles running firmwares from 1.0.0 to 11.3. This does not work on newer firmwares, as Nintendo has patched the entrypoint. It uses the Nintendo 3DS Sound app and a modified m4a file to run unsigned code. For more information on how this exploit works, read the 3DBrew page

Usage
Currently, the Soundhax exploit is used to install custom firmware, but has been used to launch The Homebrew Launcher in the past. Ideally, you should only use this entrypoint to install custom firmware, a guide for which can be found here.