When i use firebase deploy --only functions to deploy cloud functions for firebase, i discover, that this functions are deployed with the authentication flag allUsers.
How can i deploy firebase cloud function with private by default as mentioned here ?
There is no way to set this access control level of Cloud Functions through the Firebase CLI. It currently indeed always sets the access to allow all users. It sounds like a reasonable request to allow control of this though, so I'd file a feature request and possibly a PR on the repo.
For now: if you want to set this access level, you will have to do so in the Cloud console as explained in the Google Cloud documentation on controlling access on a function.