- Green Growth
- Your Consultant
|The Twitter logo is seen on a phone in this photo illustration in Washington, DC. (Photo: Alastair Paik/AFP)|
The micro-blogging site said the issue was rectified as of Sep 17, without disclosing how many users were impacted.
None of the user data was shared with partners outside the company, the San Francisco-based company said.
"This was an error and we apologise," the company said in a blog post.
"We're very sorry this happened and are taking steps to make sure we don't make a mistake like this again," Twitter added.
Social media companies, including Twitter and Facebook, have faced heat from users and regulators globally on how their platforms handle user data.
Twitter said when advertisers uploaded their marketing lists, it may have matched people on the platform to their list based on the email or phone number provided by account holders.
The company said the information was not shared with third parties, but was made available internally to allow users to receive targeted advertising.