🚨WhatsApp Security Flaw Exposed 3.5 Billion Phone Numbers
Researchers at the University of Vienna found that WhatsApp’s contact discovery feature could be abused to enumerate 3.5 billion phone numbers.
By automating checks on the web interface, they matched numbers to profiles and pulled profile photos and “about” text at scale due to missing rate limits. Meta fixed the issue in October 2024 after being alerted in April.
The team warned that scammers or regimes could have exploited the flaw, noted key-reuse patterns suggesting unauthorized clients, and called it the largest documented phone number exposure, though they deleted all collected data.
