The Heartbleed OpenSSL Vulnerability (CVE-2014-0160) was released on April 7th 2014.
What is Heartbleed?
Heartbleed is a vulnerability (bug) within the Heartbeat extension for the popular OpenSSL package and is compiled by default in within a number of Unix/Linux distributions. The vulnerability affects a component of this extension and if successfully exploited can reveal data in memory on the target host. This could include sensitive private keys and/or sensitive information such as user passwords or other data in a decrypted state.