Heartbleed vulnerability

Heartbleed is a security bug that appeared in 2014, which exposed information that was usually protected by SSL/TLS encryption. Because of a serious vulnerability that affected the OpenSSL library, attackers could steal data that was kept confidential by a type of encryption used to secure the Internet. This bug caused around 500.000 web servers (17% of all severs on the Internet) to be exposed to potential data theft.