HTC isn't the only mobile company having trouble keeping its 2015 flagship phone under wraps. XDA-Developers forum member reefur has posted photos of what's believed to be a prototype Samsung Galaxy S6 for AT&T. The tipster was understandably worried about giving it a spin, but he notes that this handset is "pretty slim" and more upscale than Galaxy S phones of the past. In addition to the expected metal frame, Samsung's usual plastic backing has been replaced with glass à la the iPhone 4 and Nexus 4 -- don't drop this, folks. There also doesn't appear to be either a removable battery or a microSD card slot, which is bound to disappoint some fans if this is what shows up at Samsung's March 1st event.