It isn't always that simple. The government sometimes discloses such information intentionally with an agreement that the briefer's name is not disclosed.
This is half the newspaper nowadays. Every journalist just repeats what some official with an impressive job title says and nobody gets to question why the story is being pushed by this person because they are never identified. It's naive to call for prosecution, this story was almost surely leaked and approved by the US State Department before it was written.
Journalists should really dig their heels in and start resisting this, but that will never happen. It's just bad journalism and they keep letting themselves get manipulated.
I don't even care about the classified information aspect of this, the classification system in the US is a complete farce and will be reformed soon, clearly nobody respects it all anymore at any level of the intel community.
Journalists without a long history of connections and experience, typically facilitated by the name/history of the "paper" they're working for, don't get to dig their heels in because they would lose access. Access is paramount, as is on record/off record confidentiality, and they are dependent on it, else they be blacklisted by their subjects of interest. All interviews and information sharing is voluntary, they can't force someone to answer a question, and they can't force someone to be interviewed, and they definitely can't force someone to tell the truth.
It is not their fault that they parrot whatever talking points politicians and their staff members. It's only on those rare occasions where sources are cultivated through long periods of time and building trust through publishing meticulously what information has been shared with them via interviews and documents, most of them being talking points of course, that they can get to the meat of the subjects. Lifting the veil of the real news stories requires years and years of trudging through just simply formatting interview transcripts into something readable and of interest.
I don't blame them one bit. It's a tough job and you're at the mercy of everyone you attempt to gather information from. It doesn't help that you're viewed as de-facto suspicious due to journalistic freedoms.