Tea, a women-only safety app, is experiencing a surge in popularity, adding 900,000 new users and reaching a total of 4 million. The app allows users to anonymously assign 'red' or 'green' flags to local men, providing a platform for sharing experiences and warnings. The app has recently topped the Apple App Store charts, indicating its growing influence in the dating and safety space. Users are citing the app's ability to identify potentially harmful individuals as a key benefit.