Mitigating clickjacking is a security issue where an attacker tricks users into clicking on malicious websites by embedding them inside iframes, but it can be easily prevented by setting the x-frame-options header in browser headers. To identify vulnerable endpoints, tools like OWASP AMASS and Security Headers Checker are used to scan for missing security headers, including x-frame-options. These tools can help automate the process of finding and fixing vulnerable endpoints, ensuring that all endpoints have the necessary security headers to prevent clickjacking attacks. The importance of having a bug bounty program and testing reproducing the issue to ensure it won't happen again is also highlighted in this case study.