2
How does Comcast’s Xfinity Wi-Fi insert an in-page popup when you login from a computer that you’ve logged in with before?
This most commonly happens when the Wi-Fi connection resets. It shows up within the current web page, then goes away after a few seconds. The page doesn’t show any Comcast hostnames. I did notice this CSS file, that went away after reloading the page. It doesn’t show on HTTPS urls, as expected.
http://d5k1a84rm5hwo.cloudfront.net/all-201407312053.css
FYI Xfinity Wi-Fi is the Wi-Fi network that is created and managed by Comcast owned equipment and allows you to connect to a hotspot when you’re away from home.