Candle wax burn. I have repaired several burned carpets, not just from the candle, but also from people trying to remove the splattered wax from the candle, using a clothing Iron and paper towel carpet fix method that’s going around on the internet. “Google is your friend”, but common sense is a prerequisite. Most synthetic carpets have a fairly low melting point. Carpets don’t like getting close and personal with a clothing Iron, or any heat source for that matter.