"Digital attackers could use the vulnerability to insert malicious code and steal data from an Android phone or an iPhone simply by placing a WhatsApp call, even if the victim did not pick up the call"

NYT:

The spyware was used to break into the phone of a London lawyer who has been involved in lawsuits that accused [an Israeli firm] of providing tools to hack the phones of Omar Abdulaziz, a Saudi dissident in Canada; a Qatari citizen; and a group of Mexican journalists and activists, the researchers said.