Some unknown hackers managed to hack into several Twitter accounts, forcing the company to send an email to users and asking them to change their passwords. Twitter announced this by tweeting using their @support account about this. Here is the link to the tweet.
If you received an email regarding a password reset on your account earlier today, check our Status blog for more info: http://t.co/m3LiGNY0
— Twitter Support (@TwitterSupport) November 8, 2012