Firebase Realtime Database Insecure Rule Warning - firebase

Question

I keep getting emails saying my database is not secure after implementing my security rules. The emails specify that any authenticated user can read/write to my database but I implemented specific access rules:
{
"rules": {
"posts": {
".read": "auth.uid !== null",
".write": "auth.uid !== null && newData.hasChildren(['score', 'quote',
'description', 'source', 'sourceType', 'ownerID', 'ownerImageURl', 'ownerUsername', 'timestamp', 'usersVoted'])",
".indexOn":["sourceType", "ownerID"],
"$postID": {
".write": "!data.hasChild('ownerID')",
"score": {
".write": "newData.isNumber() && (newData.val() === data.val() + 1 || newData.val() === data.val() - 1) && !root.child('posts').child('$postID').child('usersVoted').hasChild(auth.uid)"
},
"usersVoted": {
".write": "!data.hasChild(auth.uid)",
"$userID": {
".write": false
}
}
}
},
"users": {
".write":"auth.uid !== null && !data.hasChild(auth.uid)",
"$userID": {
".read": "auth.uid === $userID",
".write": "auth.uid === $userID"
}
},
"comments": {
".read": "auth.uid !== null",
"$postID": {
".write": "auth.uid !== null",
"$commentID": {
".write": false
}
}
}
}
}
Why does Firebase think that any user can read/write to any location in my database?
EDIT: I haven't gotten the email in a while so I think my rules are secure.

Answer 1

For example this rule for users node, is not secure:
"users": {
".write":"auth.uid !== null && !data.hasChild(auth.uid)",
"$userID": {
".read": "auth.uid === $userID",
".write": "auth.uid === $userID"
}
}
Because, this rule allows any authenticated user and non-existing user to write to your users node (not secure):
".write":"auth.uid !== null && !data.hasChild(auth.uid)",
and it overwrites this rule (as if this is meaningless now):
".write": "auth.uid === $userID"
To make it secure, users rule must look like this:
"users": {
"$userID": {
".write":"auth.uid !== null && !data.hasChild(auth.uid) && auth.uid === $userID",
".read": "auth.uid === $userID"
}
}
So fix your rules, and be careful of RULES CASCADING.