I just read this over at Wikipedia in the
Karl Rove article and I don't recall it being mentioned in any of the Rove diaries.
In 1992, Rove was fired from George H. W. Bush's 1992 presidential re-election campaign for allegedly leaking information to journalist Robert Novak.
More on Rove and Novak after the fold.
Here's a thread at MyDD on this topic.
Rove was caught for leaking to Novak in '92 and was fired by Bush Sr.
Both the Wikipedia article and the MyDD thread appear to come from this story at Bust Bob.
Oh and here is a diary from a couple weeks ago. Looks like this is common knowledge after all, but good to repeat into the current zeitgeist.