Hope they had an approved mount for that
Years ago, QF got approval for a removable camera mount to be fitted to the glareshield in front of the F/O so that it could be fed through to the IFE system. This was for use on Antarctic charter flights and it allowed those who weren't at windows to see what's happening outside (pax were rotated through window seats so that everyone got a share of the viewing).
I assume that they used this mount on this occasion for the GoPro.