Someone else moved my pieces as a Guest?

Hello there,
I was playing more or less half an our ago as a random guest from my phone in a few blitz games and all went fine for a good while (1 hour or two), then after a few in a match while I paused to think on my move, my pieces moved by themselves (and making fairly decent moves too) over and over while I was just looking!

So I looked a bit on the forum to check for someone else with a similar experience, found nothing relevant, accessed the chess page back and I was watching this other person playing other players, I could even potentially move his pieces!
Someone has any clue about what happened? Did we somehow got the "same guest account", or what else?