Fourteen million files, not four million stolen security files is closer to the truth about the OPM breach. The breach is a digital Pearl Harbour for America. The files include the ultimate disclosure form, SF-86. Its 127 pages document everything that might make you easy to blackmail, you being every US government employee past and present and apparently some CIA and FBI too. Senators and their aides, presumably too. In there are your brushes with the law, whom you sleep with, any drug use, mental institutions, and risky behaviour that would make you an easy target for America's enemies. Even your contacts with foreign nationals are disclosed. As a Chinese intelligence officer, I'd go through those contacts, punish Chinese citizens who concealed them and reward the others to keep it up.
You've been scolded for years to upgrade your passwords but the scolders themselves are the juicy target. Chuang Tzu nailed this thousands of years ago:
"In taking precautions against thieves who cut open satchels, search bags, and break open boxes, people are sure to cord and fasten them well, and to employ strong bonds and clasps; and in this they are ordinarily said to show their wisdom. When a great thief comes, however, he shoulders the box, lifts up the satchel, carries off the bag, and runs away with them, afraid only that the cords, bonds, and clasps may not be secure; and in this case what was called the wisdom (of the owners) proves to be nothing but a collecting of the things for the great thief."