Twitter said it mistakenly used customer phone numbers and email addresses, initially provided for security purposes, to display advertisements to its users. According to the Associated Press, the company claims it “inadvertently” used customer information to let advertisers match users to their own marketing lists—though Twitter says it shared no personal data with advertisers or other third parties. The company said it fixed the issue on Sept. 17 but is not disclosing how many users were affected. Facebook previously admitted to allowing advertisers to access the personal data of users and paid a $5 billion fine to the Federal Trade Commission earlier this year over its missteps on user privacy. As part of the FTC settlement, Facebook also agreed not to use phone numbers given to the platform for privacy purposes for advertising.