Technika was developed for the computer security professionals to automate common exploitative task from the browser. It acts like a standard OS shell scripting environment. You can script everything from the currently viewed page just like Greasemonkey (spawn processes, unrestricted XMLHttpRequest connections and sockets). You can autorun bookmarklets and perform safe operations on the currently viewed resource.
You can install the Technika Firefox Extension here:
Or you can explore the code here:
Technika was successfuly used to implement several Web and System related exploits that run directly from the browser. Unfortunatley their source code cannot be shown here for obvious reasons.
If you want to persist some data, use Firefox, IE or Opera persistent objects. Your bookmarklets will remain portable across all browsers as long as you support them in your code. Technika is extremely light so go ahead and install it. If you want to use Technika command console, please install Firebug.
The extension is still in Alpha although it is mostly usable and quite stable.
You can read more on the home page here: