A few years ago, Timehop posts were all the rage on my social media feeds. The service plumbs the depths of your social media archives to resurface moments you may have enjoyed throughout your history on a social media platform—a photo of you and your friends at graduation, a great joke you made five years ago, a check-in from a vacation you took a few years back. It was a fad that people briefly loved and later forgot about, an increasingly common life cycle for some social media companies. 

The novelty app has now become a significant security issue for its users. The app recently posted a blog post to its website indicating that it was subject to a data breach on July 4 that exposed 21 million users’ personal information, including email addresses and phone numbers for over 4 million users.