GHSA-x287-5c68-36wp: OpenWISP IPAM has broken object-level authorization: ExportSubnetView lets a member of one organization export another organization's subnet and all its IP addresses

OpenWISP IPAM is multi-tenant: every Subnet belongs to an organization, and API access is scoped to the organizations a user belongs to. The CSV export endpoint, ExportSubnetView, omits the organization-membership check that its import sibling performs, and loads the subnet by primary key with no organization filter. An authenticated user who is a member of one organization can therefore export a subnet belonging to another organization — its name, CIDR, organization slug and every IP address in it — by issuing an export request for that subnet’s id.