If you do read the paper, you see that the universal machine U expects both a description of the simulated machine T, and a description of the input to T. The e

If you do read the paper, you see that the universal machine U expects both a description of the simulated machine T, and a description of the input to T. The exploit is that they can cause arbitrary code execution not by changing the former but the latter. They also suggest a fix to U that makes it robust against exploits in the description of T's input.