WhatsApp is urging users to update the app after it was targeted by hackers.

Scroll on to find out how to make sure your phone is safe from the vulnerability.

Visit BusinessInsider.com for more stories.

WhatsApp is urging people to update the app immediately after it was targeted by hackers installing sophisticated spyware on users' phones, giving the hackers access to a trove of data.

The security vulnerability has been fixed in updated versions of WhatsApp released in recent days, but some users will need to manually update the app to get protected.

It is not yet known how many of WhatsApp's 1.5 billion users were targeted by the bad actors, who installed the surveillance technology — developed by Israel's NSO Group — by phoning the target through WhatsApp's call functionality.

Read more: WhatsApp was hacked and attackers installed spyware on people's phones

"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," Facebook, which owns WhatsApp, said.

Scroll on to find out how to make sure your phone is safe from the vulnerability.