blow someone's cover

verb2

1. •
   To reveal that someone's behavior, situation, or identity has been fabricated or deliberately misrepresented for an ulterior motive.

   • Iskander's role as a G.A.M. operative was secret—until I unwittingly blew his cover that day. — 2007
2. •
   [with oneself] To reveal that one has fabricated or deliberately misrepresented one's own behavior, situation, or identity for an ulterior motive.