Spring Boot and React together

 Two good examples on how to serve your Spring Boot application with ReactJS:

https://github.com/kantega/react-and-spring

https://dzone.com/articles/spring-boot-and-react-happily-ever-after

CSP (Content-Security-Policy)

 And here's the detailed page on content-security-policy: https://content-security-policy.com/

CORS

This is the best article I read on CORS: https://blog.logrocket.com/the-ultimate-guide-to-enabling-cross-origin-resource-sharing-cors/