Am I reading correctly that you can not update the firmware through the web interface? Looks like you can update the wifi firmware though the web interface. Looks like this updates the actual web GUI as well.. Maybe there just are not many core charger changes that would ever need a firmware update? either way a little disappointing that you can not.
For enhanced security, updating the firmware on the OpenEVSE safety controller must be done with a physical connection using an AVR compatible programmer. Updating the WiFi firmware and User Interface (non-safety) can be done over the air. The firmware on the safety controller does not change very frequently.
If you wish to implement different security measures on you own station, it is possible make a small physical modification to allow software loading via serial and install a bootloader on the OpenEVSE controller. http://blog.lincomatic.com/?p=2056
If you wish to then upload safety firmware over WiFi then program over the OpenEVSE-WiFi serial connection the Wifi firmware would also need some modifications. https://github.com/jeelabs/esp-link