Facebook has published a security notice on its official Security sub-domain warning WhatsApp subscribers using a version older than v2.19.134 on Android and v2.19.51 on iOS to update the app to the latest version available immediately.

This is after the Financial Times established (via BBC) that attackers had created an exploit that allows them to install surveillance software on a phone without the user’s knowledge. All they have to do is make a voice call to your WhatsApp account and they are in.

You don’t even have to answer or reject the call to give the attackers permission to install this software. Even more frightening is that you won’t see the said missed call in the log, meaning you’ll never know what happened behind the scenes. Scary stuff for an app that poses as a secure avenue for communicating with friends thanks to the much-hyped end-to-end encryption.

On the brighter side, WhatsApp has already patched this exploit, hence the push for the billions using the app to update to the latest versions available on Android and iOS. As long as your installed version on the former is at least 2.19.134 and the latter is at least version 2.19.51, you should be fine.

For users of WhatsApp for Business, be sure to upgrade to at least version 2.19.44 on Android and version 2.19.51 on iOS. Those using Windows Phone should update to version 2.18.348 and above while Tizen users should switch to version 2.18.15 and above.

Once again, be sure to grab the patched version right away.

Related: How to use WhatsApp Web