The track - originally titled 'Pleasure You' - is believed to be from a 2010 studio session and features vocals from Don Philip, a former tourmate of Spears who recently auditioned in front of the popstar on The X Factor USA.
Philip, who was unsuccessful on the Fox reality show, posted the track on his SoundCloud page.
He took to his Facebook account following his X Factor appearance to admit that he hadn't performed well, while also taking a dig at Spears.
He wrote: "Back to real life… all my demons released… i totally crocked when the pressure was on… at least I didnt shave my head… my vocal chords tightened up like a snake around a mouse."
Spears joins fellow new judge Demi Lovato along with returning stars Simon Cowell and LA Reid for X Factor USA's second season, which premieres on September 12 on Fox.
Watch a promo for the second season of The X Factor USA below: