https://techcrunch.com/2019/12/24/twitter-android-bug-phone-numbers/

A security researcher said he has matched 17 million phone numbers to Twitter user accounts by exploiting a flaw in Twitter’s Android app.

Ibrahim Balic found that it was possible to upload entire lists of generated phone numbers through Twitter’s contacts upload feature. “If you upload your phone number, it fetches user data in return,” he told TechCrunch.