As of November 2015 there are bootloaders available in which a “rescue mode” is integrated.
The ‘rescue mode’ allows you to approach the receiver via the network (webbrowser) and re-flash it.
By pressing the menu- or power-button, depending your receiver, the STB will boot into ‘Rescue Mode’
Output on the STB:
Please, be aware that your receiver needs a complete new firmware flash, so it is wise to backup your information.