WhatsApp users are being urged to update to the latest version of the app after a spyware attack was discovered.
A vulnerability in the Facebook-owned app allowed hackers to install technology on people's phones.
WhatsApp has released an update to close the exploit.
It comes after a 'select number' of users are said to have been targeted through the app's call function.
Researchers believe the exploit was used as recently as Sunday to target a human rights lawyer.
WhatsApp has just pushed out updates to close a vulnerability. We believe an attacker tried (and was blocked by WhatsApp) to exploit it as recently as yesterday to target a human rights lawyer. Now is a great time to update your WhatsApp software https://t.co/pJvjFMy2aw https://t.co/e8VQUraZWQ
— Citizen Lab (@citizenlab) May 13, 2019
The Financial Times reported that the vulnerability was developed by Israeli cyber intelligence firm NSO Group.
However, it's not clear who was responsible for the attack.
A WhatsApp spokesperson said: “WhatsApp encourages people to upgrade to the latest version of our app, as well as keep their mobile operating system up to date, to protect against potential targeted exploits designed to compromise information stored on mobile devices.
"We are constantly working alongside industry partners to provide the latest security enhancements to help protect our users.”