Allowing access based on mapped key

Question

It's a simple and common use case of security rule, but cannot make it work. I have a document orgs/fooOrg on my Firestore(not RTDB), and it contains an object

{
  "members": {
    "fooUser": true
  }
}

and the rule applied is

service cloud.firestore {
  match /databases/{database}/documents {
    match /orgs/{orgId} {
      allow read: if "fooUser" in resource.data.members;
    }
  }
}

I expect all the document in orgs collection should be able to be read; however, the server says Error: Missing or insufficient permissions as a result of running

firebase.firestore().doc('orgs/fooOrg').get()

on a browser (using v4.5.0 and v4.5.1). Even

allow read: if resource.data.members["fooUser"] == true;

fails, too. What went wrong?

In my understanding, this should work according to this document https://firebase.google.com/docs/firestore/security/secure-data#evaluating_documents_currently_in_the_database

I believe that it was working like a week ago. All the sudden, my working code started to generate the error, so I wrote this MCVE and tested on several different projects.

In addition, I found similar issues below, but a bit different from them, so not sure if it's the same reason (a bug on Firestore)

Firestore security rules based on map values (My case, even getting a simple document fails)

Firestore read rules with self condition (This case uses a value of a map. My case, a key is used)

Answer 1

Now seems that the issue is solved without changing code. No announcement, but seems that something is fixed by Firestore side.