Xfinity gateway management portal at 10.0.0.1 provides a certificate only valid for “myrouter.io”

As it says in the topic name. After a network hiccup prompted me to check on my gateway settings, I found that attempting to access the management portal at 10.0.0.1 caused a security knockback in Firefox because the site was trying to use a certificate for “myrouter.io”. Attempting to connect over insecure http autoforwarded to https and the same error. The security knockback was not present when I accessed the page in Chrome.

I cannot find any information about this domain being associated with comcast online, save a reddit post from last month by someone with a similar issue. Is this legitimate, or should I consider my device compromised?