Help Identify please?

I noticed this in my tank today sucking on the glass. It looks like a white starfish to me with brown in the middle. I have never put anything like this in my tank and the live rock has been in the tank for about 6 months now. Is it a starfish and is it reef safe or should I get him out if there?
 
You'll be suprised at what just "shows up"...

I found a 3" or so urchin cruising my tank one night... That I hadn't put in there... Over three years after I set my tank up...
 
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