Unknown Phone On Wifi

Earlier this week I got a notice in the xfinity app  that a suspicious website had been blocked on one of my connected devices. When I viewed the device, it was an unknown to me Android phone  listed as  an Xiaomi Redmi A2+. 

I recently relocated and this is new service that is only a few months old and I have only had one house guest during that time to whom I provided the password,  and they confirmed that this device was unfamiliar to them as well. 

Obviously I immediately changed the password  for the Wi-Fi as well as the Wi-Fi name and paused  and subsequently removed that device from my wi-fi,  however,  when I reached out to the Xfinity tech services via text  , the tech provided me with an explanation that  did very little to reassure me.  Among other things, the tech said,




"While running troubleshooting steps, I see that there was an issue with the provisioning. I have further run the troubleshooting steps to fix that from my end, and going forward, you will not face this issue again.Yes, that has been taken care of for you. Due to network intermittency and incomplete provisioning that occurred, it will not happen again. Please be assured of it.An issue with provisioning typically means there is a delay or problem in setting up a device that could have had weak spots in the network. However, I have completed the diagnostics, and this has been fixed for you."




From my admittedly limited understanding of provisioning errors  as well as Googling a bit,  this does not seem like a plausible explanation for why an unknown device would be  connected to my password protected wi-fi.  I'm hoping for either  some demystification on  what this tech means and how an unknown device could have been connected to my wi-fi, or else  some solidarity that it seems the tech may have just been trying to reassure me in order to quickly close a ticket.