That's totally fair, but it raises a followup question because from what I can see, MagicBell has user accounts.

So that's also a unique identifier that they could use to prevent collisions. They could have a randomized ID generated locally for this "promotional" extension, and if a user creates an account on MagicBell at that point they could migrate them over to an official user ID.

If this is being tied to a real backend service, I'm almost more confused why it's important to transmit my session cookies around.