[928S]

"I have included a service bulletin for GM vehicles (including your 2008 CTS). They are correct....even if they replace the headlamp, the new one will likely have the same problem in times of high humidity. This condition is not caused by a water leak, but by high humidity. We often drill a tiny hole on the inside of the lens to release the humidity. GM would probably not approve, but it does solve the problem. If the problem persists even in times of low humidity, maybe there is a more serious problem (but I doubt it). It usually will not affect your visibility as the heat from the bulb will evaporate the water. Let me know what they say."

Michael 514, the note from your salesman is dead on target. I have not asked my dealer to drill vent holes, as the occasional (high-humidity) condensation harmlessly comes and goes without leaving a trace.