Mozilla admitted that they had a mishap and may have had 44,000 usernames and passwords from addons.mozilla.org leaked. The security leak was actually located by a Mozilla employee. As of yet, there has been no sign that the data was actually obtained by an attacking party. But it is highly recommended that if you receive any email from Mozilla requesting you to change or enter your username and/or password, to ignore this message.
Mozilla will never send you this request.