I develop a macOS application (App Store distribution) that uses CloudKit to synchronize records between iOS and macOS devices. One of my customers receives the following error message on macOS Mojave 10.14.0 when trying to fetch records from CloudKit:
"The certificate for this server is invalid. You might be connecting to a server that is pretending to be “gateway-carry.icloud.com” which could put your confidential information at risk."
He sent me a screenshot of his Apple certificates, which look fine to me: