Sergiu Gatlan* says Twitter has had to apologise after users’ phone numbers and email addresses were misused to target advertising.
Twitter says that some of its users’ phone numbers and email addresses provided for account security like two-factor authentication may have been used accidentally for ad targeting.
“We recently discovered that when you provided an email address or phone number for safety or security purposes (for example, two-factor authentication) this data may have inadvertently been used for advertising purposes, specifically in our Tailored Audiences and Partner Audiences advertising system,” Twitter said.
The information has been shared publicly since Twitter does not know the exact number of people who were affected in this incident and the company wanted to make everyone aware of what happened.
Issue addressed as of 17 September
“No personal data was ever shared externally with our partners or any other third parties,” added Twitter.
“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.”
Twitter’s Tailored Audiences is an advertising product designed to allow advertisers from all over the world to send targeted ads to customers they have in their marketing lists based on information such as phone numbers and email addresses.
The Partner Audiences advertising system, on the other hand, makes it possible for advertisers to target users from lists provided by third-party partners.
“We’re very sorry this happened and are taking steps to make sure we don’t make a mistake like this again,” Twitter said.
“When an advertiser uploaded their marketing list, we may have matched people on Twitter to their list based on the email or phone number the Twitter account holder provided for safety and security purposes,” states Twitter’s apology statement.
The company apologised for this error and says that it’s taking measures to make sure that a similar mistake will not happen again.
Customers who want to ask for more info on this incident can contact Twitter’s Office of Data Protection.
Facebook’s 2FA info mishap
Something similar happened last year when, as Gizmodo’s Kashmir Hill discovered, Facebook built complex advertising profiles for all its users containing everything from their two-factor authentication phone numbers to info harvested from their friends’ profiles.
Later, Facebook used the phone numbers its users added for two-factor authentication as an additional targeting vector for various advertisers using its platform to deliver targeted ads.
This security mishap was subsequently discovered by a research team after the phone numbers added to test accounts were actively being targeted by advertisers after just a couple of weeks.
A Facebook spokesperson told Hill at the time that the company used “the information people provide to offer a better, more personalised experience on Facebook, including ads”.
“We are clear about how we use the information we collect, including the contact information that people upload or add to their own accounts.”
“You can manage and delete the contact information you’ve uploaded at any time.”
* Sergiu Gatlan is security and tech news reporter at Bleeping Computer. He tweets at @serghei.
This article first appeared at www.bleepingcomputer.com.
