webext_boilerplate

Web extension boilerplate files for web application testers.

This is a near minimum code base for creating your own web extension.

Temporarily Load

This code is unsigned, so you can't load it like a normal web extension. Unless you are using a development version of a browser, you have to install it temporarily. Restarting the browser will require you to re-load the plugin.

• Instructions for installing in Firefox
• Instructions for Chrome

How it works

The src/manifest.json file registers a content script src/script.js. The content script will run in every frame, at page load. The content script gets it's own scope but shares the DOM with the web page. So it adds JavaScript to the DOM of the web page. The added JavaScript shares the scope of the web page and will execute first.

As a proof of concept, the script augments the functionality of document.write with a console.log of arguments.

	// example code to dump all arguments to document.write
	document.write = new Proxy(document.write, {
		apply: function(_func, _doc, args) {
			console.group(`[**] document.write.apply arguments`);
				for (const arg of args) {
					console.dir(arg);
				}
			console.groupEnd();
			return Reflect.apply(...arguments);
		}
	});

Replace that code with what ever you want and it will run first in all frames.