The Wall Street Journal revisits the November 2003 story of the leaked Senate Judiciary Committee memos. When that story first broke I predicted that the most basic of security procedures (not implemented) was likely what made it possible for Republican staffer Manuel Miranda to view the work of Democratic staffers. I was right.
In addition it turns out that was not the first time there had been unauthorized access of data on Committee servers. Essentially the same thing happened in 1996, though the he roles were reversed, with Democratic staffers having a look at the work of Republican Committee staffers.