If you haven't changed your Minecraft password in some time, you may want to – especially if you've been contacted by someone attempting to get your information. Apparently, over 1800 usernames and passwords have been leaked to the internet by 'phishers', which are people who try to trick others into giving them their account information. Sometimes, you don't even have to respond. Information can be taken from you by simply clicking on a link.
Here's what Mojang, Minecraft's developer, had to say on the subject:
"No! We haven’t been hacked. A bunch of bad people have tricked some of our users into disclosing their account information. We’ve emailed everyone affected, and reset all compromised passwords. If you haven’t received an email from us, you don’t need to worry.
No-one has gained access to the Mojang mainframe. Even if they did, we store your passwords in a super encrypted format. Honestly, you don’t need to panic.”
Make sure to stay safe on the internet. While it's a great resource and tool, there's also a great capacity for people to do mean things like this.