Tattletale
noun
One who tattles (reports others' wrongdoings), often a child seeking attention.
One who gossips, often for the sake of attention.
Synonyms: gossip, rumourmonger, narc, snitch, tattler, whistle-blower
verb
To act as a tattletale; to tell on; to give away, reveal, or expose.
adjective
Telltale; giveaway