According to a tweet from Twitter support, the company identified an issue caused by a third-party app affecting some users, but wouldn’t specify whether this was directly related to the hack.  

— Twitter Support (@Support) March 15, 2017 BBC North America, Amnesty International and the European Parliament were among the Twitter accounts impacted by the hack. The hack is a good reminder to check your Twitter account and determine which third-party apps have access. To do this from a web browser, click on your profile picture in the top right corner, and go to “Settings and Privacy.” Scroll down along the left navigation menu until you get to Apps. Clicking on that will show you what apps have access to your Twitter feed. Now’s a good time to start cleaning up. If you see an app you haven’t used for a while or just aren’t comfortable using any longer, you can revoke access. For example, my account still allowed access to TwitPic, which shut down in 2014. Oops. Also, before you allow any service third-party access to your Twitter account, make sure to confirm it’s legit. When in doubt, deny access.

— TheCounter (@thecounter) March 15, 2017  

— BBC North America (@BBCNorthAmerica) March 15, 2017

— European Parliament (@Europarl_EN) March 15, 2017