IF an individual were to release or expose classified information an investigation is launched into what happened and how serious was the compromise. The range of penalities and actions are wide ranging. Actions could be as simple as additional training, disciplinary actions if it was willfully done. You are correct, if classified information is mishandled one could lose their clearance but it is not necessairly automatic. At least that was the way it was the last time I worked in the classified environment but that was over 25 yers ago so things may have changed since then.