What is the Facebook data leak involving 53 crore users including Indians?

Phone numbers, full names, locations, birthdates and bios of 53 crore Facebook users globally, including 60 lakh Indians, have been leaked online for free. Facebook says this is old data that was reported in 2019 and the issue was fixed in August 2019. Only a couple of years old, this data could still provide valuable information to cybercriminals, experts said.