> We investigate a range of potential sources of PII, finding that phone numbers and email addresses added as profile attributes, those provided for security pu

> We investigate a range of potential sources of PII, finding that phone numbers and email addresses added as profile attributes, those provided for security purposes such as two-factor authentication, those provided to the Facebook Messenger app for the purpose of messaging, and those included in friends’ uploaded contact databases are all used by Facebook to allow advertisers to target users. These findings hold despite all the relevant privacy controls on our test accounts being set to their most private settings. Very frustrating!