Snyk has integrated its website security scanner with WebPageTest, providing a free security score for websites that run a speed test and performance metrics through this integration. The security score is calculated based on the presence of vulnerable JavaScript libraries and missing or recommended HTTP security headers, with scores ranging from A+ to F depending on the severity of the issues found. The Snyk website scanner assesses website security by checking for specific HTTP security headers and detecting vulnerabilities in JavaScript libraries, providing detailed results that help developers identify areas for improvement.