Heartbleed
A checker (site and tool) for CVE-2014-0160
...The project illustrates how a malformed heartbeat request could coax vulnerable servers into leaking memory contents, including potentially sensitive data. Because it’s small and self-contained, it’s often used as a reference to understand the vulnerability mechanics without wading through large codebases. The repo also serves as a historical snapshot of a watershed moment in modern Internet security and the practical lessons it forced the industry to learn. Developers and security engineers alike can study it to better appreciate protocol hardening, input validation, and defense-in-depth strategies.