No and yes.
No in the traditional way of a mesh screen insert in the exhaust like most sport atv or dirtbikes.
Yes, in the design of the stock muffler. The fact that the muffler outlet comes down and kicks out 90 degrees does the same as a traditional spark arrestor. That won't allow any ignited gases to flame out.
If you're asking because you are riding somewhere that requires a spark arrestor, and you have the stock muffler still, you are completely legal.
Essentially you can not have a through and through muffler, like a dirt bike or sport quad would.
Having talked with a local DNR guy, he told me his test is this: can I shave a stick all the way through your exhaust without restriction. If yes, ticket. If no, you're good.
A stock Polaris exhaust would be a no, because of the placement an 90 degree turn on the outlet.