However i was confused if there was a need to connect a cable to 53. As is already has a connection to the WiFi shield by the ICSP Header I assume it handles it already, since it worked previously with all devices.
There is no SS on the ICSP header tho - Only SCK/MOSI/MISO and Reset/Pwr/Gnd.
So if you're going to use 53 and the shield does not plug in the Mega dual-row header, then and jumper is needed to where SS is on the shield.