Already provided in another thread, Novak asked and was told she worked for the CIA by the CIA.
They never claimed that her employment at the CIA was classified since it would be pointless to attempt to keep the identity of someone who works at the CIA Headquarters secret. The law protects the identity of covert agents as opposed to protecting the identities of CIA employees just like it protects the identity of FBI agents working in a counter-terrorism capacity as opposed to FBI agents in general.
The key here is that the CIA didn't publically discuss her covert status and they took clear steps to keep her status as a NOC agent who worked in the Directorate of Operations (now known as the National Cladestine Service) secret thus they did attempt to keep her covert status secret. There are many people who drive into CIA Headquarters under the cover of being CIA employees (i.e., a secretary) and who when at the CIA are operating as covert agents. There is no way to tell how many of the employees who enter and leave CIA Headquarters are covert agents because the CIA is intelligent enough to know that the best way to disguise the identity of covert agents who work out of CIA Headquarters is to admit that they are employees of the CIA when asked and to not publicize their employment when no one asks. To do otherwise sends up red flags and since the CIA has no ability to teleport CIA agents from one point on the earth to another I doubt very much they would be stupid enough to think that they could keep people traveling to and from CIA Headquarters a secret. Our enemies know where the CIA HQ is located and are quite capable of monitoring who goes into and leaves there.
Until the CIA gains the ability to teleport agents from one point on the earth (i.e., their homes) to another point on the earth (CIA HQ) then I suspect that they will use the cover of being a CIA employee to disguise the identity of their covert agents who work out of their Headquarters.