Disable Firefox update notification

To add a policy, follow the steps:

1. Go to the firefox installation directory (for any supported OS).
2. Create a directory called distribution.
3. Change directory into distribution.
4. Create a file called policies.json. And paste this code

{
    "policies": {
        "DisableAppUpdate": true
    }
}

    Save the file, and quit the editor.

5. Restart Firefox if it's already running.
6. To confirm, you can go to the URL about:policies and check if there's an entry like this

Policy Name     Policy Value
DisableAppUpdate    true