Explore the critical security vulnerabilities arising from cross-domain script inclusion in web applications. Delve into an often-overlooked attack vector that affects a significant number of websites, potentially exposing sensitive user information. Learn how attackers can exploit HTML's disregard for the Same-origin Policy to include dynamic scripts from vulnerable sites, gaining unauthorized access to personal data, CSRF tokens, and even full account compromises. Examine the findings of a comprehensive study on 150 top-ranked domains, revealing that a third utilize dynamic JavaScript, with over 80% susceptible to data leakage through remote script inclusion. Discover various attack techniques, defensive measures, and an efficient detection mechanism in the form of a browser extension. Gain insights into protecting web applications from these vulnerabilities through proper implementation of Content Security Policies and secure handling of dynamic scripts.