Hard to tell from the picture, but it resembles a Pentaster species from the Asteroid class of Sea stars. A few species inside this class can be considered somewhat "reef safe," although most grow to large sizes, have quite an appetite and will devour almost anything that gets in their way such as coral, sponges, algae, other inverts and some even love munching on clams.
Best thing to do would be to get it out and bring it back to your LFS where the
LR was purchased from. Ask them if they know of or have seen them before, and what you should do with it from there on. My recommendation is for it to come out, Sea stars spend their whole lives on surfaces eating and scraping away at many things in the wild. This is why only a select few species will make little to no impact on an established reef system. If it is currently a FOWLR system, then the need for it to come out quickly will not be as great.