As the content Scripts guide notes, content Scripts don't see changes made to the DOM by Scripts loaded by web pages. This means that, for example, if a web page loads a library like jQuery, content Scripts won't be able to use it, and have to load their own copy. Conversely, Scripts loaded by web pages can't see changes made by content Scripts....developer you should consider that scripts running in arbitrary web pages...isolation between content scripts and scripts loaded by web pages is...