Secure JavaScript URL validation is crucial to prevent malicious script injection and server-side request forgery (SSRF) attacks in JavaScript applications. Implementing URL validation checks whether URLs follow proper syntax, strengthening security against exploits and eliminating bugs. Developers should use the `new URL()` constructor function to validate URLs, which supports Node.js runtime and most browsers. Regex literals and constructors can also be used for URL validation, but are error-prone and time-consuming. Snyk detects vulnerable open-source packages and provides a top 10 JavaScript vulnerabilities cheat sheet. To mitigate SSRF attacks, developers should restrict protocols, set up applications to not pass URLs without oversight, and use allow and deny lists to filter and control mechanisms.