Twitter reported that it could use the personal data of users for personalized advertising without their permission due to problems in the settings of the social network, DW reported. 

The company claims that it recently discovered problems in the app, due to which the choice of settings by the user did not work properly.

“The company said "certain data" of mobile users such as country code may have been shared with advertising partners since May 2018 "even if you didn't give us permission to do so. Twitter also said since September 2018 it may have shown ads "based on inferences" made about users' devices, without consent,” the source noted.