Twitter does not have separate development, test, staging, and production environments. At least 5,000 employees had privileged access to production systems.
* insert shocked pikatchu face *
More in 
https://twitter.com/AvidHalaby/status/1602128747225923585
Unfortunately, this happens too often and therefore is unsurprising.
For those on Android, Fritter is a great app that lets you use Twitter without an account! It’s also in F-Droid.
I also want to mention that this doesn’t just affect your data; but also could result in rogue employees taking over accounts you trust and post fake or misleading information (especially if you follow journalists!)