It's an X (across-the-line) capacitor, almost certainly being used as a snubber. For across-the-line and snubber networks metalized film/paper or foil+paper are still the cat's meow. They have well understood failure modes. Ceramics are also rated as X safety capacitors in some circumstances. This is not the job for an electrolytic or an unpolarized electrolytic. It is the job for a safety rated capacitor. Tim.