Comment by refulgentis

There isn't one, that's sort of the thing. The invisible hand of downvotes is the only thing indicating that in the thread, and thus only indirectly. We only have two choices, a magical tampering detector that bricks the whole thing (maybe desirable for some applications, if it never false positive'd), or, the vulnerability.

I'm not even sure a tampering detector would help. If this can happen, I'm fairly sure someone would figure out how to do the ocr by appending components externally.