A new report suggests the Xbox Series X mystery port seen on the back of the console is used for expandable storage through CompactFlash Express (CFexpress) card.
A report from Thurrott suggests that the small, rectangular slot seen next to a power cord port, two USB 3.0 ports, a digital audio port and HDMI out port is actually for a CFexpress card, a next-gen CF card capable of 1750MB/s read and 1400MB/s write speeds.
It seems CFexpress cards are expensive at the moment with a 512GB card selling at £460 GBP. We are speculating the price of the CFexpress card will drop in the build up to the Xbox Series X launch, making them more affordable.