Any number of issues, depending on the network architecture and other variables. Is there storage mounted to the container? Or network access to/from the container for admin access, etc? Anything else on the dmz rail in the blast radius of the infected server?

I’ve seen far too many compromised Wordpress installations to ever consider installing it in my home dmz.

Cloudflare’s default setup is to proxy your traffic but that’s easily disabled with a click of the admin’s mouse. Of course disabling their proxy service exposes the origin IP’s, server certs, etc. but the point is that you use Cloudflare services the way you want to; it’s not a Boolean “cloudflare or no Cloudflare”.