You left out the part about how you use them as a reverse proxy, which is decoupled from DNS. One is coincidental; the other required.
If they can inject script, they can also snoop on all your cleartext traffic without you knowing....
Indeed. I have several domains using cf for dns only and they don't/can't inject anything into those sites.
Oh gosh I didn’t enable anything like that also. I just wanted the nameservers in order to serve the bucket under my subdomain. What else is there I wonder?