Unknown GUI on my gateway

Hey there, @ddb545j! Thank you so much for taking the time to reach out to us here on the Xfinity Forums. That certainly is alarming to see an unknown device connected to your network, and we would be happy to look into troubleshooting with you further on concern. Can you please send us a DM to get started?

Please send us a DM with your full name and address to Xfinity Support.
To send a direct message:
Click "Sign In" if necessary
Click the "Direct Message" icon or  https://forums.xfinity.com/direct-messaging
Click the "New message" (pen and paper) icon
The "To:" line prompts you to "Type the name of a person". Instead, type "Xfinity Support" there.
As you are typing a drop-down list appears. Select "Xfinity Support" from that list.
A "Xfinity Support" graphic replaces the "To:" line.
Type your message in the text area near the bottom of the window 
Press Enter to send it

@ddb545j @XfinityAdrienne 

Please circle back here and post any possible solutions for the issue here in these open public forums so that all readers here may benefit from the exchange / info. This is in keeping with the spirit for which these public help forums were originally intended. Thank you.