‘Largest Data Leak in History’: WhatsApp Flaw Exposed Billions of Users

Austrian researchers used a WhatsApp contact-lookup flaw to map 3.5 billion phone numbers, revealing how basic metadata can build a directory of accounts.

It began as a small curiosity and ultimately exposed phone numbers for nearly half the planet.

A team of Austrian researchers has uncovered a major weakness in WhatsApp, revealing how a basic contact-lookup function can be exploited to create a global directory of users. By pushing WhatsApp’s contact discovery tool far beyond typical use, the researchers confirmed 3.5 billion active phone numbers linked to WhatsApp accounts.

In the research paper, they noted that the exposure would have been “the largest data leak in history, had it not been collated as part of a responsibly-conducted research study.”

The researchers stated that the data for many accounts “contains phone numbers, timestamps, about text, profile pictures, and public ...