Twitter says there is no evidence of a breach, but the error would have allowed any snoopers inside the system to scoop up unprotected passwords with ease. Typically, passwords are "hashed" before they are stored, a process which transforms them password into a unique series of numbers and letters that can't be translated back into the actually sequence of numbers and letters you type in. This prevents hackers from snagging a phrase they can try on your other accounts.
Even with no evidence of an actual breach, this bug serves as a good reminder for some basic security hygiene. Use unique passwords for every service you use; a password manager can help you keep track of them all. Turn on two-factor authentication where available (it is available on Twitter). And while you're at it, go look at the apps that have access to your account. These apps, if they're insecure themselves, can offer hackers a limited way into your account without ever having to figure out your password.
Stay safe out there!
