A vulnerability named Heartbleed was discovered in the software that protects most web sites.
What is Heartbleed?
The Heartbleed Bug (also known as CVE-2014-0160) is a serious vulnerability in the popular OpenSSL cryptographic software library. This weakness allows stealing the information protected, under normal conditions, by the SSL/TLS encryption used to secure the Internet. SSL/TLS provides communication security and privacy over the Internet for applications such as web, email, instant messaging (IM) and some virtual private networks (VPNs).