There were several details of this article that dropped my jaw. At the risk of spoiling some of the suspense for you:

– this WD HDD has 4 ARM CPU cores (granted, clocked at only 150 MHz)

– the author was able to hook into the DMA code of the firmware to return arbitrary data to SATA read requests

– the author injected a linux kernel (but no userspace unfortunately) into the firmware and booted it on one of the ARM cores

Originally shared by Alun Jones (pengfold)

Wow. Just wow!