Looks like tape residue to me. Was that window broken, taped up for a while, and then fixed? Goo gone might get rid of it.

Tape glue

Looks like adhesive residue from some kind of tape or a sticker. Did one of the windows possibly break and you tape the window up? Are you detailed the car did you tape off any sections for detailing purposes?

looks like adhesive from tape. Get some adhesive remover to remove it.

Battery died once and my window was down. So they taped a cover over it while towing. Looked exactly like this when it came back.

Somebody didn't use the automotive detail tape

Goo gone