Because arbiters do not replicate data, they do not have a copy of a replica set's credentials, and therefore refuse all authentication attempts when auth is required. As a result certain operations required for basic maintenance and for integration with MMS, that were previousily available via the localhost exception, are no longer possible.
This change makes following operations available to clients that have access to an arbiter via the localhost exception:
3.0.0, 3.0.1, and 3.0.2
The fix is included in the 3.0.3 production release.