Hackers used a WhatsApp vulnerability to remotely installed a surveillance program on cellular phones, WhatsApp admitted Tuesday morning.
Following the incident, WhatsApp issued a security update for its 1.5 billion users.
The program installed after users dialed a receiver’s phone number, regardless of whether the call was answered or not.
It is not yet clear how many users were affected by the breach, which was discovered earlier this month.
“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,” the company said in a statement.
“We are constantly working alongside industry partners to provide the latest security enhancements to help protect our users.”