Asterina starfish. As far as good or bad, it depends who you ask. They are generally safe although there are certain varieties that will eat some corals.
I give up....what am I supposed to be looking at. I see in-focus in the upper right quadrant, but the rest looks like vasoline smeared on the lens. I see no starfish!!!
There are two very common small "hitchhiker" starfish. One is asteria starfish...small and chunky. The other is mini brittle starfish. Brittle starfish are reefsafe. Asteria are hit or miss. If they are white to light tan/gray, they should be OK. If black or dark color, keep an eye on them.