WhatsApp Privacy Flaw Exposed: 3.5 Billion Numbers Collected by Researchers
WhatsApp’s simplicity — requiring only a phone number to connect with someone — has long driven its global popularity. However, this same system created a major privacy vulnerability. Austrian researchers have revealed that they were able to collect the phone numbers of all 3.5 billion WhatsApp users, along with public profile photos for 57% of them and profile text for 29%.
How the Data Was Collected
No hacking was involved. The researchers used WhatsApp Web like any regular user. By entering phone numbers, they could confirm if the account was active and view public profile photos and text. Using automated tools, they checked roughly 100 million phone numbers per hour earlier this year.
WhatsApp’s parent company, Meta, was initially warned about this flaw in 2017. Despite the warning, no action was taken until the Austrian team raised the issue again in April 2025. By October, Meta implemented rate limits to prevent large-scale automated data collection.
Meta stated that the exposed data counts as “basic publicly available information” and emphasized that users who set their profile photo or status to private were not affected. The company also confirmed that no sensitive or private data was accessed and found no evidence of malicious use of this method.\
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Implications
This incident highlights the need for users to review their privacy settings and for platforms to proactively address vulnerabilities, even in basic features like phone number visibility.
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WhatsApp Privacy Flaw: Researchers Access 3.5 Billion Phone Numbers
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Austrian researchers collected 3.5 billion WhatsApp numbers and public profiles. Meta has now added protections, but users are urged to review privacy settings.
