What The Guardian did was entirely ethical. Whisper told its
reporters highly newsworthy facts about its own service. The
information was all on the record. The Guardian reported it. It
would have been a journalistic lapse for the paper not to have
told readers what it had learned.
In fact, even had the sessions been off the record, or as Primack
asserts, implicitly private, The Guardian would have had to give
serious consideration to burning its sources if it couldn’t
otherwise confirm the information. I’d argue that the right of the
public to know that it is being gravely misled clearly outweighs
the agreement by the paper not to publish that information.