Hackers jailbreak permanent mods onto Super Mario World save files

Incredible hack perpetually alters game through nothing but controller input.

https://youtu.be/Ixu8tn__91E

The practice of hacking standard Super Mario World cartridges on stock Super Nintendo hardware has come a long way in a short time. Three years ago, it required a robot entering thousands of button presses per second to insert arbitrary code on top of the game. By last year, streamer SethBling was proving that this kind of code insertion was possible for a human acting with pixel-perfect precision.
Now, SethBling and others in the SMW hacking community have taken things a step further, permanently writing a full hex editor and gameplay mods onto a stock Super Mario World cartridge using nothing but standard controller inputs.

SethBling's ten-minute video explaining the entire "jailbreaking" process is a must-watch for anyone interested in the particulars of perpetually altering a 25-year-old game without any special hardware. In short, the jailbreak builds on an exploit discovered by Cooper Harrsyn that lets players write data directly to the small, 256-byte save files that are permanently stored on the Super Mario World cartridge.

If you arrange that data just right, you can trick the game into running custom code just by loading the save file, saving you the trouble of manually jailbreaking the game every time you start it up. With that exploit in hand, Harasyn and SethBling worked together to create a compact, on-screen hex editor that could be loaded from one of the game's save files. From there, players can edit the system RAM to alter the game state in a lot of ways, giving Mario arbitrary power-ups, messing with color palettes, or even beating levels with the press of a button.

More importantly, though, the hex editor can be used to write additional in-game mods that can live in that small save file space. Those mods can run on top of every frame of the game, running a short code loop on top of the standard game loop. In the video, the hackers show off a clever mod that gives Mario telekensis powers as a proof of concept, (coded with the help of TASbot team member p4plus2). Another mod adds support for the SNES mouse to the game.
It took SethBling about an hour of painstaking, in-game work to get the hex editor installed on an actual Super Mario World cartridge save file (following the method detailed here). From there, it takes about 10 minutes to copy that data to a backup cartridge (by exploiting the persistence of some portions of RAM between system resets).

If you don't want to go through all that trouble, you can use this SRAM file with the Bizhawk emulator to test out the hex editor and simulated on-cartridge modding for yourself. Or maybe SethBling will continue making copies of his jailbroken cartridge and sell them to interested parties online. Hint, hint!