repo/testing/firefox/files/policies.json

{
    "policies": {
        "DisableAppUpdate": true,
        "DisableFirefoxStudies": true,
        "DisablePocket": true,
        "DisableTelemetry": true,
        "DontCheckDefaultBrowser": true,
        "DisableFeedbackCommands": true,
        "DisableFirefoxAccounts": true,
        "DisableFirefoxScreenshots": true,
        "DisableFirefoxStudies": true,
        "DisableMasterPasswordCreation": true,
        "DisableSetDesktopBackground": true,
        "DisableSystemAddonUpdate": true,
        "DontCheckDefaultBrowser": true,
        "ExtensionUpdate": false,
        "NetworkPrediction": false,
        "OverridePostUpdatePage": "",
        "CaptivePortal": false
    }
}