loose lip(s)

loose lip(s)

The practice, habit, or manner of speaking too frequently and/or without discretion, especially as might unintentionally lead to revealing private or sensitive information to others. You've got a very loose lip, son. You'd do well to learn to keep it shut! The details of this project are extremely confidential, so make sure you don't have loose lips about it.
See also: loose
Farlex Dictionary of Idioms.
See also:
  • have a loose tongue
  • loose talk
  • foot-in-mouth disease
  • fall through the cracks
  • slip between the cracks
  • slip through the cracks
  • slip through the net
  • leave good (enough) alone
  • by coincidence
  • coincidence