<script>alert(1+1);</script>
<span style="font-size: 300px;"><marquee>hello</marquee></span>
<span style="font-size: 300px;"><marquee>hello</marquee></span>
<img src="kitten.jpg" onerror="alert('meow!')">
:^)
Edit: meh, stupid CSP…
I guess rot would be no problem, but the surface would probably liquefy during the day, and freeze at night, turning into a cheese sea (or maybe an under-crust sea beneath frozen-cheese ice crust?) affected by earth-induced tides, and possibly internal tidal heating which liquefies the inside of the moon too.