Venting directly into the attic is a bad situation even if it's allowed by local code (which is unlikely). Dumping moisture and lint into an attic is not a good thing. Perhaps the ducting is loose from the exhaust hood.

It's not.

A dryer must be vented to the outside.

Moisture will do damage/rot wood and or promote mold growth.

Lint is highly combustible. You don't want an attic or crawl space loaded with lint.

Our vent has come off before. It does quickly fill the attic with lint. I found some of the problematic spots and covered them with foil tape. It might also be a good idea to replace some of the sections if they are the weird foil type instead of the stronger aluminum type!

Thank you everyone for your comments. When we looked at the house, I saw that the dryer was backed up to an inside wall. I assumed (shame on me) that it was vented to the attic and outside. Our inspector missed this among several other big problems. One contractor suggested running the vent from the existing lead in the attic to the soffit and a lint collector. I think this would be ugly. The other choice so far is to do the same but have the collector in the attic. I cannot imagine having to go up there to clean this thing out.