Microblogging platform Twitter has admitted that users data like email addresses and phone numbers that had been provided by them for security purposes may have been "inadvertently" used for advertising purposes.
The US-based company noted that it could not say "with certainty" how many people were impacted by this, but asserted that "no personal data was ever shared externally with our partners or any other third parties".
"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 in a statement.
It added that as of September 17, it has addressed the issue that allowed this to occur and it is 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," it added.
The company declined to comment on the impact of the development on users in India.
Twitter, in its statement, explained that when an advertiser uploaded their marketing list, it may have matched people on Twitter to that list based on the email or phone number that the Twitter user had provided for safety and security purposes.
"This was an error and we apologise...We cannot say with certainty how many people were impacted by this, but in an effort to be transparent, we wanted to make everyone aware," it said.
In June quarter, Twitter had an average monetisable daily active usage (mDAU) of 139 million (29 million in the US and 110 million from international markets). This is against an mDAU of 122 million in the same period of the previous year, and 134 million in the previous quarter this year.
Twitter does not provide country-specific user numbers.