blow someone's cover
US /bloʊ ˈsʌm.wʌnz ˈkʌv.ər/
UK /bloʊ ˈsʌm.wʌnz ˈkʌv.ər/
1.
to reveal someone's true identity or secret activity, especially when they are trying to keep it hidden
:
•
The spy's partner accidentally blew his cover by calling him by his real name in public.
•
She tried to keep her new job a secret, but her excited friend blew her cover on social media.