The Milky Way's disk is indeed warped. The current leading explanation is that the warp is due to the net gravitational force of a nearby satellite galaxy, the Large Magellanic Cloud. The Large Magellanic Cloud orbits the Milky Way in an extended orbit extending 180 kpc from the Galactic center, bringing it about 50 kpc from the Galactic plane and sometimes crossing the plane. The Galactic warp may well have been a consequence of the most recent pericentric passage ~1.5 Gyr ago.

There is no evidence to suggest that the Milky Way's dark matter halo is responsible for the warp in its disk.