Twitter Slip-Up Spills MFA Phone Numbers, Emails to Advertisers

Twitter account holders who provided an email address or phone number to enable multifactor authentication may have had their data used for advertising purposes, Twitter reports.

The issue lies in Tailored Audiences and Partner Audiences, an advertising system offered to help marketers better connect with people on the platform. Tailored Audiences lets companies aim ads at customers based on their own marketing lists, containing email addresses and phone numbers obtained outside Twitter. Advertisers can upload marketing lists to Twitter and advertise to accounts linked to the same email address — people who already know the brand.

Twitter found that when advertisers uploaded marketing lists, they were accidentally matched with email addresses and phone numbers provided to the social media giant for account security. As a result, users' contact data was used in targeted ads without their knowledge.

It's unknown how many people were affected by the mistake, Twitter reports, noting that no personal data was externally shared with its partners or third parties. This issue was fixed on September 17 and the company is no longer using security contact information for advertising.

Read more details here.

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