Hello defur. Thanks for visiting and posting on our Forum. I can assist with signing you out of all devices with your account signed in. You'll want to change your password first. For instructions to change your password, please visit: Reset Your Xfinity Password - Xfinity Support
Please reach out to me via private message and include your full name and service address, so I can assist you. You can click my name (ComcastJoeTru) to view my profile, and then click "Send a private message" in the upper right.