Useful for those stuck on v5.5.2, but have 'backups' from their v5.5.1 or earlier consoles!
@modrobert writes: "dimok has posted a brief tutorial and coded Linux tools to inject WFS blocks via USB over at gbatemp.net. This is primarily for those who updated to firmware 5.5.2 by mistake and are interested in restoring HBL or haxchi on their Wii U. I have uploaded a complete pack with a save exploit here. The procedure is pretty advanced, and the tools are compiled for a Linux (32bit) system, to use on Windows (or Mac) you need to compile/port the source code yourself. This also requires an SEEPROM dump from the target console."
OFFICIAL RELEASE SOURCE: --> http://gbatemp.net/threads/wfs-usb-block-injector.479785/
NEWS SOURCE: WiiU WFS USB Block Injector Released (via) EurAsia