WhatsApp asks users to upgrade app after 'serious' security breach

WhatsApp on Tuesday encouraged its users to upgrade the app to plug a security breach that allowed sophisticated attackers to sneak spyware into phones, in the latest trouble for its parent Facebook.

The vulnerability -- first reported by the Financial Times, and fixed in the latest WhatsApp update -- allowed hackers to insert malicious software on phones by calling the target using the app, which is used by 1.5 billion people around the world.

"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," a spokesperson said in a statement to AFP.

The breach is the latest in a series of issues troubling WhatsApp's parent Facebook, which has faced intense criticism for allowing its users' data to be harvested by research companies and over its slow response to Russia using the platform as a means to spread disinformation during the 2016 US election campaign.

The WhatsApp spyware is sophisticated and "would be available to only advanced and highly motivated actors", the company said, adding that a "select number of users were targeted".