WhatsApp’s contact-discovery flaw let researchers match 3.5 billion phone numbers to active accounts. By exploiting the absence of rate limits, they checked vast number ranges to see which were registered. They also found that many users exposed their profile photos and About texts publicly. The team even identified millions of accounts in countries where WhatsApp i…WhatsApp’s contact-discovery flaw let researchers match 3.5 billion phone numbers to active accounts. By exploiting the absence of rate limits, they checked vast number ranges to see which were registered. They also found that many users exposed their profile photos and About texts publicly. The team even identified millions of accounts in countries where WhatsApp i…