str2hax is an exploit that was found by Fullmetal5. It's an implementation of CVE-2009-0689 for the Wii.
You can find more information about the str2hax exploit on its Github page
and in this GBAtemp thread.
Leseratte took a Wiimmfi patcher and embedded it within this str2hax exploit, which allows you to run a Wiimmfi patcher
just by opening the EULA / License Agreement screen within the Wii settings while using a special DNS server.
There's no archive or program that needs to be downloaded in order to use str2hax.
All you need to do is go into the Wii Network settings, set the DNS server to Manual, then enter the following DNS IP:
Then, save the connection, make a connection test, then click on the third button "Agreement / Contract" (EU) / "User Agreements" (US). A Wiimmfi page should now appear.
Wait a while for the patcher to load (usually it takes about 1.5 minutes), and then the inserted game should boot with a Wiimmfi patch included.
If you run into UPnP-related issues (like the patcher getting stuck at the "Init network ..." or "add UPnP port forward" steps for more than 10 seconds)
you can press the Minus button on your Wii Remote, or the Y button on your Gamecube controller as soon as the patcher loads to get around that.
If that happens to you, please let us know so we can fix this issue for the future.