Twitter has reported that each of its 330 million users immediately change their passwords after discovering an error that exposed them momentarily in plain text.
According to Twitter, the error has already been corrected, and an internal investigation revealed "no indication of non-compliance or misuse by anyone."
On the side of caution
Having said that, Twitter has urged its users to err on the safe side, stating that "as a precaution, we ask you to consider changing your password in all services in which you have used this password".
Enabling login verification is also recommended for your Twitter settings, since it prevents someone from logging into your account from a new device without a verification code (sent to your phone).
We also recommend that you consider using an administrator and password generator, as it will automatically create a unique and exceptionally strong password for each of your accounts.