Moisture in headlight

Hey guys former mustang owner here who has a friend with an 03' GT. His drivers side headlight is starting to get moisture in it, like alot. The car has never been hit this just happen all of a sudden. Could there be any reason for this, and resolutions. Just wanna see if I could help him out.

Thanks!

There's a leak in the seam somewhere. Dry it out, then reseal the seams with RTV or silicon.

Great thank you for the help.

That would be covered under warranty if he is still under it.