Twitter recently discovered a problem with its ads settings. If you clicked on or viewed an ad on its mobile app since May 2018, data like your country code may have been shared with advertisers. Since September 2018, Twitter “may have” showed you ads based on inferences about your smartphone, again without permission.
The company fixed the problem on August 5, 2019. Twitter is continuing its investigation to find out how many people were affected. The blog post mentions how powerless users are, saying:
What is there for you to do? Aside from checking your settings, we don’t believe there is anything for you to do.
Translation: There isn’t anything you can do, because settings don’t matter if the company improperly runs its business. Although maybe you could say that advertising is its business. You can contact Twitter’s Office of Data Protection using this form.