This exploit works because the sandbox designer failed to forbid bytecode loading, which is known to be much more unsafe than accepting only source files. I bel

This exploit works because the sandbox designer failed to forbid bytecode loading, which is known to be much more unsafe than accepting only source files. I believe there are several known ways to crash a VM by loading bad bytecode, for instance. Patch loadbuffer() et al. to make it refuse bytecode files and you're safe.