Twitter is the latest company to admit to a privacy faux pas. In a statement Twitter informed users that phone numbers and email addresses intended for security may have inadvertently been used for advertising purposes.

Twitter uses Tailored Audiences, a customized version of an industry-standard platform designed to allow “advertisers to target ads to customers based on the advertiser’s own marketing lists (e.g., email addresses or phone numbers they have compiled). Partner Audiences allows advertisers to use the same Tailored Audiences features to target ads to audiences provided by third-party partners.”

Twitter goes on to say they may have matched users with their marketing list based on contact info that was provided for security purposes, such as two-factor authentication. The company is unsure how many users were impacted, although they are confident no data was shared with third-parties, including their advertising partners.

“As of September 17, we have addressed the issue that allowed this to occur and are no longer using phone numbers or email addresses collected for safety or security purposes for advertising.

“We’re very sorry this happened and are taking steps to make sure we don’t make a mistake like this again. If you have any questions, you may contact Twitter’s Office of Data Protection through this form.”