As you're building out a web application, you'll have to be very careful with what is being exposed in the browser. In this lesson, let me show you the issues of using exposeLocalsToBrowser() by inspecting the source code of our pages. To fix these problems, we'll go over two different solutions of sanitizing objects before we send it to the browser. Finally, let's also discuss the options that can be passed into exposeLocalsToBrowser such as keys.