Most regulators shutdown automatically if over-current or over-temperature, most regulators can take 25V or so on the input if it wasn't for thermal considerations, so the worst that should happen is it will shutdown after a while. If you find the regulator's part number and google for its datasheet it will provide more definitive information.
The more current you circuitry takes the less voltage the regulator will handle without overheating note, so the answer probably depends on the external circuitry you attach to the board. This is partly why there is no definitive answer.