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Privacy Flaw in Signal and WhatsApp Allows User Tracking via Delivery Receipts

First seen 13 Dec 2025, 09:51 UTC • Pogowasright

•24.3

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A new tool named Device Activity Tracker exposes a privacy flaw in WhatsApp and Signal, enabling attackers to monitor user activity using only their phone number. This vulnerability leverages delivery receipts, which are typically benign, to covertly track users. The research originates from the University of Vienna and SBA Research.

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Privacy Flaw in Signal and WhatsApp Allows User Tracking via Delivery Receipts

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