Currently when someone is added as follow to a document default subtypes
are computed if no specific subtypes are given to the subscription. However
if internal subtypes are set as default those are added to all new
followers. It should take into account customers and shared users and avoid
adding them internal subtypes.
Customers and shared users are not notified of messages using an internal
subtype. So currently there is no information leak. However with this fix
we ensure internal subtypes are not followed by external people even if
no notification is created.
From #14704, backport of 03ac47b9
Pedro M. Baeza
88a9ee2565