Yes, EXPOSED is a Scrabble word!

Letter values in Scrabble US: E 1, X 8, P 3, O 1, S 1, E 1, D 2.

Is it a valid word?

EXPOSED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

expose or make accessible to some action or influence
make known to the public information that was previously known only to a few people or that was meant to be kept a secret
to show, make visible or apparent
remove all or part of one's clothes to show one's body
disclose to view as by removing a cover
put in a dangerous, disadvantageous, or difficult position
expose to light, of photographic film
expose while ridiculing; especially of pretentious or false claims and ideas
abandon by leaving out in the open air

Also: let on, bring out, give away, let out.