breaking my own promise now, but I will try to be a bit more explanatory in my post. (and I hate first letter capitalization after a period, so excuse me for all lowercasing)

look into Zigbee networks and permit / deny join… by default, if your hub in this case allows (permits) devices to join this will happen. there should be a option in the app / hub to permit new devices or detect or something like it. as I do not have the hub / app i cannot say where it is exactly, but there should be one.

also, by default, any Zigbee clients (and also hubs by force) will try to join any open networks if they are not part of any. since there is no way to configure a bulb for instance, to which Zigbee network or should join, it by default joins the first open network it sees and stays there until it is reset or kicked out.

I am guessing your hub connected to a device named Chris yes, and informed you through the app as it is connected to the account you are referring to. this is what you saw in the notification when it entered and when it left by reset or force on the client side.

it has nothing to do with your cloud account, but you probably have a permit join Zigbee network in the hub as i mentioned before.

have a good day, and take a look in your app or hub when you have a chance for that setting.

(edit, btw: there is not much of a security issue here, as the client cannot talk to other devices or force your hub to do anything , so it’s more of an annoyance than anything else, at least until there is some sort of exploit for the Zigbee protocol and the hub, which there is none of as far as I know)