Twitch's security has been compromised and infortmation on "some" user's has been accessed. The amount of users affected has not been revealed, but Twitch has responded to the security breach with an entire wipe of saved information from users.
This means that every password and stream key has been reset. Twitch has even disassociated user accounts from Twitter and YouTube to prevent any further security breach.
If you have a Twitch account and attempt to log in, you will be met with a prompt to create a new password. The streaming service is also recommending that users change their password on any site that uses the same or similar password. If your account was breached Twitch will contact you with additional details.
Here is the official statement from Twitch:
We are writing to let you know that there may have been unauthorized access to some Twitch user account information.
For your protection, we have expired passwords and stream keys and have disconnected accounts from Twitter and YouTube. As a result, you will be prompted to create a new password the next time you attempt to log into your Twitch account.
We also recommend that you change your password at any website where you use the same or a similar password. We will communicate directly with affected users with additional details.
[Twitch]
