JavaScript has become the language of choice for the logic that drives web browser extensions. Web browser extensions enhance the underlying capabilities of the browser itself. For example, the LastPass Password Manager extension [10] allows a user with an account to not only store all of their passwords in one place but offers secure password generation and automatic online form filling as well. Another popular extension, NoScript [14], automatically blocks JavaScript from executing in a user’s browser unless it is given explicit permission to do so. This allows a user to block malicious or unknown origins from executing code while allowing known origins to execute freely.