Selena Gomez Bares Bum As She Works On "Secret Project"

Selena Gomez has been increasingly brazen about her Instagram snapshots, showing off more and more skin with every post. 

In her latest photo, Gomez, 21, shows off her toned bootie as she poses in a sexy, sheer black ensemble. The pop star holds up her brunette locks as she stares seductively into a mirror. 

She captioned the snapshot: "...Secret project."

Gomez has yet to reveal what her 'secret project' might be, but the hint suggests she's getting back to work -- perhaps on a new music video or film. While the singer performed a few concerts in Texas and attended the Sundance Film Festival earlier this year, she's kept a relatively low-profile since cancelling her Australian tour in December. At the time, she told her fans that she needed to take a step back from work to "spend some time on [herself.]"  In January, she secretly entered rehab to deal with issues unrelated to alcohol or substance abuse. 

We're happy to see Selena back at work and looking so healthy! Any ideas about what her 'secret project' could be?