Seems my Google foo or Bing foo for that matter isn't strong enough to find the bug right now.
It was one bug years ago, where update checks or submission of telemetry information (the last one could even be opt-in) went to a google domain and by mistake would include the normal cookies it would send for that domain.
I do remember it didn't apply to everyone, so that could be because of the telemetry opt-in or because not everyone regularly visits that Google domain.
Also I don't know how long that bug existed though.
Anyway, a long time ago. But my point is, it could happen again in theory.