On Tuesday, October 8, 2019, Twitter representatives admittedthat the company inadvertently used email addresses and phone numbers used for security purposes (for example, for two-factor authentication) to display targeted advertising.
The fact is that when companies and users promote their advertising on Twitter, they can filter the advertising audience based on a number of criteria. And by mistake, phone numbers of users and their mailing addresses were available through the company's internal advertising systems – Tailored Audiences and Partner Audiences.
It is reported that the problem was fixed as early as September 17, and the company states that no other user data has been transferred to the company's partners and other third parties. The exact number of users affected by this error is unknown to company representatives.
Interestingly, last year, Facebook made exactly the same mistake. Then researchers from Northeastern University and Princeton University have noticedthat the phone numbers required for 2FA are used by advertisers to target ads. At the same time, Facebook representatives confirmed to reporters Gizmodothat the social network uses the information provided by users to personalize their experience, including by displaying more relevant ads.