One who exposes wrongdoing

• Person with inside information making public some illicit activity
• One discloses having broken elbow in Canadian ski resort
• Wrongdoer's bane
• Company informer
• Inside informer
• Employee who calls out bad practices, say

Wikipedia Word definitions in Wikipedia
A whistleblower ( whistle-blower or whistle blower ) is a person who exposes any kind of information or activity that is deemed illegal, unethical , or not correct within an organization that is either private or public. The information of alleged wrongdoing ...

WordNet Word definitions in WordNet
n. an informant who exposes wrongdoing within an organization in the hope of stopping it; "the law gives little protection to whistleblowers who feel the public has a right to know what is going on"; "the whistleblower was fired for exposing the conditions ...