Massive credential spills on the Dark Web and hacked data exposed by way of cloud misconfigurations. The entire population of Ecuador was impacted by an open database with rich, detailed life information collected from public-sector sources by a marketing analytics company. Facebook had a bad year for breaches, including the December emergence of a hacked database containing the names, phone numbers and Facebook user IDs of 267 million platform users. In September, an open server was discovered leaking hundreds of millions of Facebook user phone numbers.
Source: https://threatpost.com/top-10-breaches-leaky-server-2019/151386/