Tea, a provocative dating app designed to let women anonymously ask or warn each other about men they’d encountered, rocketed to the top spot on the U.S. Apple App Store this week.

A dating safety app that allows women to do background checks on men and anonymously share "red flag" behaviour has been hacked, exposing thousands of members' images, posts and comments.

The purpose of a woman adding a man's "dating data" and "dating history" would, in theory, build community and help other women share "red flags" or warnings about people they say they've dated or an...