We recently learned that the way Mozilla Firefox stores cached data may have resulted in non-public information being inadvertently stored in the browser's cache. This means that if you accessed Twitter from a shared or public computer via Mozilla Firefox and took actions like downloading your Twitter data archive or sending or receiving media via Direct Message, this information may have been stored in the browser’s cache even after you logged out of Twitter. The Mozilla Firefox browser’s cache retention period is set to 7 days and after that time the information should have automatically been removed from the cache. This issue did not impact people using other browsers like Safari or Chrome. 

While cache data is only stored locally on Firefox browser users' devices, we have implemented a change so that Mozilla Firefox no longer stores Twitter data in the cache at all. If you use, or have used, a public or shared computer to access Twitter, we encourage you to clear the browser cache before logging out, and to be cautious about the personal information you download on a computer that other people use.

We’re very sorry this happened. We recognize and appreciate the trust you place in us, and are committed to earning that trust every day. If you have any questions or concerns regarding this incident, you can contact Twitter’s Data Protection Officer by completing the online form located here.

Updated on April 3, 2020