An error in the way the passwords were handled meant some were stored in easily readable form, said Twitter.
The passwords should have been put through a procedure called “hashing” making them very difficult to read. Security experts said the way Twitter handled the potential breach was “encouraging”.
The bug caused the passwords to be stored on an internal computer log before the hashing process was completed.
We are sharing this information to help people make an informed decision about their account security. We didn’t have to, but believe it’s the right thing to do. https://t.co/yVKOqnlITA
— Parag Agrawal (@paraga) 3 mai 2018
Read entire article Twitter users told to change passwords after internal leak | BBC