One of their KPIs is: "Percent of users who have or create an FxAccount via Send, Why: representation of % of any service users who might be amenable to an upsell"

From this it seems that their moneymaker is the new Firefox account creations that will be driven by this service, to whom they can then upsell. But it doesn't state what they are trying to upsell. Anyone got any idea what that might be?