According to Tamron Hall on the Today show, Twitter passwords were possibly compromised recently. This explains the NFL tweet earlier this week where an unauthorized Tweet was posted erroneously announcing NFL commissioner Roger Goodell’s death. Other high profile accounts were also compromised last week.
To avoid this happening to you, enable 2-Step login verification on your Twitter account! This sends you a text message to verify the login is authorized. Even if a hacker has your password, it would be very hard for them to obtain the SMS text message code required to finish the login. I strongly recommend using 2-step verification especially if you are a high profile account or celebrity! Other sites like facebook and google have two step verification as well.
The passwords were likely not taken directly from Twitter, but likely from malware on the end user’s computer. You should also verify the apps you have authorized to have access to your twitter account on this page.
Update 6/11/2016- According to People Christina Grimmie’s Twitter Account Hacked Hours After Her Death with a tweet that said “The End”
It is vital that you change your password on twitter!