Most of my chargers came with the devices, and I assume Apple checks those pretty carefully. I have a couple bricks from Belkin or other well-known brands that have never had issues with security. I don't think most charger companies are at risk for this, but I think the very cheapest ones might. For example, the cheapest TVs are monetized by telemetry because the purchase price alone doesn't make for a sustainable business model. I would think the same thing might happen with chargers.