According to Rap-Up.com, Ciara is on the Ludacris  “How Low” remix.

There will be three or four official remixes to Luda’s chart-topping hit. One features Rick Ross and Twista, the other has Ciara and Pitbull, and Fabolous appears on a third. Ciara sings part of the hook on her remix and adds her own verse, as do all the rappers.