StackPath EdgeRules

[mjda]

I'm wondering if any of you use StackPath CDN and, if so, what EdgeRules you use. Tonight I noticed that a member registered on my forum with an IP address owned by StackPath LLC. This lead me to believe that they registered on the site using cdn.domain.com/register rather than domain.com/register. I'm unsure how to keep that from happening, but don't want to disable the CDN completely, either.

Any advice here?