A Rat told Cliff May as I pointed out above.
Novak described a long conversation with an administration official (he later stated one who did not work in the WH) and during that conversation when Novak brought up Wilson's recent op-ed piece, this official mentioned how wifey had recommended him. That's it. Novak called the CIA, got a pro-forma "don't publish" but they didn't press it as Novak said they would have if she was, for instance, an undercover agent, so he wrote it up.
Gee, well, if it's all that tidy, then...
Why is there an investigation wasting our money and time?