Whatsapp has released an updated version after it was left defenseless due to hackers who found a way to sneak in surveillance software through voice calls, the Financial Times has reported.

The unfortunate part is that the victims would be unaware of the hacking. Every user is therefore advised to update their application versions so as to get rid of this vulnerability as soon as possible.

According to the Financial Times, the hackers targeted a UK based human rights lawyer who then sounded the alarm after receiving several suspicious calls from a stranger. Early discovery was made in May.

Although WhatsApp messages are encrypted, access can be gained once the messages reach one’s phone, leaving their sent and received messages vulnerable. Whatsapp has acted against this, releasing an updated version on Monday. Whatsapp users are therefore urged to update their applications immediately.

-Financial Times