Extension does three things with the tabs - Get the current tab info for page url to match with the list, open a new tab for settings page, third - to clear history on window close though there is a function it doesn't work as intended and is known within firefox community. So, to make "history clear on window close" work, extension monitors if its the last tab closed and performs cleanup. You are welcome to check the source code. Wish, firefox has an easy solution.