Secret

Without ?key=secret:

{
    "minimumVersion": 1,
    "packages": [
        {
            "name": "NotSecret",
            "title": "NotSecret",
            "version": "2.1",
            "location": "notsecret.json",
            "priority": 1
        }
    ]
}

WITH ?key=secret:

{
    "minimumVersion": 1,
    "packages": [
        {
            "name": "NotSecret",
            "title": "NotSecret",
            "version": "2.1",
            "location": "notsecret.json",
            "priority": 1
        },
        {
            "name": "Secret",
            "title": "Secret",
            "version": "1.5",
            "location": "secretdirectory/secret.json",
            "priority": 1
        }
    ]
}