Just remembered another report about a vote-counting machine with a security problem. Can't remember enough details to find the original report, but the guy found that the QR code the machine was scanning to read the vote did not have any kind of replay protection, and that although the ballots were printed on special paper, the machine did not have any verification of the paper being fed into it, and would accept plain photocopy paper. Meaning that all that would be needed to "hack" that particular machine, if the report was accurate, would have been to get hold of a ballot belonging to someone you know voted for your preferred candidates, and have it for 20-30 seconds of secrecy, long enough to make one photocopy before giving it back to the voter. Easy to do if the voter and the poll worker are in cahoots. And then you can run off 50, 100, 250 copies of that ballot and stuff the ballot box. Would be caught on a recount... probably. But it shouldn't be possible to do that sort of thing in the first place.

The simpler the machine, the better. As I said in my other comment, I'm about ready to go back to locked wooden boxes myself, opened and counted in full view with cameras rolling.