The 18-year-old "Drivers License" hitmaker and singer-songwriter Gray appeared in a TikTok video dancing on a bed as another re-recorded track, "You Belong With Me", played.
"You ok? no. fearless (taylor's version) comes out tonight," Gray captioned the footage. "here's a sneak peek of one of our favorites."
Swift previously leaked new versions of "Love Story", "Mr. Perfectly Fine", a previously unheard collaboration with Maren Morris, called "You All Over Me", and "Wildest Dreams".
Last weekend, Swift revealed the track listing for the Fearless bonus album, explaining it will include 27 tracks from the project's recording sessions.
She is in the process of re-recording her old hits to thwart the new rights owners' efforts to make money off the originals.
Last year, the "Shake It Off" singer was legally allowed to re-record her first five albums, which Scooter Braun gained ownership of last year following his $330 million deal with Big Machine Label Group. Braun later sold her masters to a company called Shamrock Holdings for $300 million (£259 million).
"I've spoken a lot about why I'm remaking my first six albums, but the way I've chosen to do this will hopefully illuminate where I'm coming from," she said. "Artists should own their own work for so many reasons, but the most screamingly obvious one is that the artist is the only one who really knows that body of work."