Quark fried, blown capacitor...

[BrianG]

Well, the inrush current spark would be an issue if the current had to go through the ESC circuit to get from the battery to the cap, but since the caps are usually close to the battery input, that wouldn't be the case.

A cap can supply a LOT of energy and discharge very high currents, but an ESC is a high current device specifically capable of high currents.

The voltage on a cap can only be as high as the battery supplying it. It's not like a coil where you can have a reverse polarity inductive kickback many times higher than the input voltage.