Dubbed "Heartbleed", the vulnerability exists in the popular OpenSSL cryptographic software library used by millions of companies like Twitter, Facebook, and Google, to provide security and privacy over the internet for applications such as web, email, instant messaging and some virtual private networks.

http://www.smh.com.au/it-pro/security-it/newly-discovered-encryption-flaw-a-big-deal-say-security-experts-20140408-zqsb0.html