this is nothing ownCloud related but in my opinion that grave to post it as an announcement in here.
At the moment there is a grave security bug in the SSL/TLS implementation of OpenSSL which is used in your webservers SSL implementation or in SSH.
An attacker is able to read stuff like passwords or private keys from the memory of vulnerable clients or server without authentication. Everything currently in your memory could be affected.
So update your client or server ASAP (better yesterday than tomorrow) and change sensitive data like passwords or private keys.
More infos are available here: