By default, Cisco and Juniper routers (and likely others too, those are just the ones I can speak of) will advertise all bgp learned routes to all bgp peers unl

By default, Cisco and Juniper routers (and likely others too, those are just the ones I can speak of) will advertise all bgp learned routes to all bgp peers unless you specify a route map/export policy. Leaking a route would imply you’re advertising the route to a peer that you’ve otherwise not intended to, either due to a misconfiguration or by not configuring things at all.