Earlier this week a researcher showed how to circumvent Windows RT's code integrity mechanism and now someone else has already published a tool online that lets you run unsigned code with the push of a button. Created by netham45, the Windows RT Jailbreak tool can be downloaded over at the XDA Developers forum.
The tool is simply a batch file that automates the jailbreak process discovered by the hacker clrokr, who was able to change a setting in the Windows RT kernel after tracking down the right value to open up the types of apps that the OS can run. As we outlined before, the exploit is limited by the fact that the setting needs to be changed each time the PC boots up (it can’t be permanently altered on devices enabled with Secure Boot), and it only works for unsigned ARM desktop apps.
At the time of the discovery, we noted that the hack opens up possibilities for a homebrew scene full of ARM desktop apps for Windows RT and thus the Microsoft Surface. Previously, only very technically-savvy users would be able to reproduce clrokr’s method; now a tool exists that does most of the work.
More details at The Next Web. At this point it's unknown how Microsoft will react to this, and whether the company will attempt to patch this issue.