WhatsApp users have been warned their messages aren't safe after the app was hacked.
The app, owned by Facebook, confirmed on Tuesday there had been a serious security breach and some personal data may have been accessed.
Users have been warned to update the app "out of an abundance of caution", but did not say how many users have been affected.
It did admit both Android and iPhone users have been targeted.
iPhone users who want to update their app should launch the app store, tap the updates button at the bottom right of the screen, find WhatsApp and tap update.
Android users need to open the Google Play Store, go to menu and tap my apps and games. Then tap update all, or find the specific you want to update and tap update.
Some users' apps may have updated already if their phone settings allow apps to update automatically.
Once that's done users should be safe, but it's probably smart to install some increased security measures for the future.
Ensuring your WhatsApp messages do not backup to Google Drive or iCloud is a good start, as well as ensuring two factor authentication.
Two factor authentication would mean users would have to do something extra when they log in or change settings, like entering a code or answering a security question.
It may seem annoying, but it's a small price to pay for safety.