Twitter says it inadvertently used private information provided by users for security purposes to help advertisers target them with ads. Users provided their phone numbers and email addresses in order to enable certain security features, such as two-factor authentication, to prevent accounts from being hijacked. Twitter said the error that allowed the security information to be used was fixed as of September 17. It did not say how long the error was ongoing, and how many people were affected. Gizmodo revealed that Facebook was intentionally doing so last year.”]
Source: https://gizmodo.com/twitter-misused-private-security-info-to-help-advertise-1838887411