The vulnerability was fixed on Friday, but it’s a blow to a company that prides itself on providing secure communications to its 1.5 billion users, using end-to-end encryption.

The details: The security hole let an attacker read messages on the target’s device. It used WhatsApp’s voice calling feature to call someone and then install surveillance software, even if the call was not picked up. The call would often disappear from the device’s call log. It was discovered earlier this month by WhatsApp’s own security team. It targeted specific users and was developed by Israeli security company NSO Group, according to the Financial Times.

Who’s behind it? Its development is likely to have been directed by a government, and the suspected attacks were targeted to specific individuals, WhatsApp said. It didn’t name any of them. 

What do I need to do? Make sure you’re using the latest version of WhatsApp. Although your phone might have auto-updated since Friday already, it’s worth checking. For Android devices, that involves opening the Google Play store and looking in “My Apps & Games” to see if WhatsApp needs updating or not. The latest version is 2.19.134. For iOS, you need to check the App Store and make sure you’re using WhatsApp version 2.19.51.

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