There was a time, not all that long ago, when the Pentagon sank tens of millions of dollars into remote-controlled lightning guns that it hoped would fry insurgent bombs before they killed any more troops. Now, disassembled parts from the one-time wonder-weapons are being sold on eBay. At least one buyer snatched up the gear, hoping to use it in his latest art project for Burning Man.

All of which would make for a funny little story, if that buyer didn’t discover that the multimillion dollar “Joint  Improvised Explosive Device Neutralizers,” or JINs, were kluged together from third-rate commercial electronics, and controlled by open Wi-Fi signals. In other words, the Pentagon didn’t just overpay for a flawed weapon. On the off-chance the JIN ever worked, the insurgents could control it, too.

“This is the hack of all hacks,” says Cody Oliver, a freelance technologist in San Francisco. “And this is what they were selling to the government? Holy shit.”

OK, that story is kind of funny, too. In its own dark way.

It started one day last April, Oliver says. He was brainstorming with sometime-employer, Elon Musk, about their next project for Burning Man. For the last three years, Oliver had built for Musk “art cars” — tricked-out jalopies — in the shape of rocket ships that Musk then drove around the festival. (Musk is the founder of the rocket-maker SpaceX, among other firms.) This year, Oliver suggested something different — a remote-controlled art car. Musk liked the idea. So Oliver started trolling eBay for robotic control systems.

He figured he’d get something industrial grade, that already had all the safety and interference issues sorted out. Oliver quickly found a pair of Omnitech Robotics NGCM1 controllers — the kind of high-end electronics that ordinarily sold for tens, if not, hundreds of thousands of dollars. Oliver bought a pair for a thousand bucks. He sent his dad down to a nondescript warehouse in Tucson, Arizona to pick the stuff up.

Oliver knew there was something different about these controllers almost as soon as he took them out of the crate. The steering wheel was outfitted with black buttons labeled “Enable Weapon” and “Weapon On.” In the center was a big red button marked, “STOP!”