Call linux command from a html page in Firefox or from Firefox extension

Question

Is there any possibily that I can have a html page with button, that when the user click it, it will run linux command on the local machine?

If it is not possible, then is it possible to have a firefox extension that monitor a url, and if the url appear, the extension itself will run a linux command on the local machine?

The html page is run on Firefox on Linux platform.

Answer 1

I wrote such an extension a while ago. The person who asked me to agreed to release it under an open-source license, and here's a mirror. Updating it to work under the latest version of Firefox is left as an exercise to the reader.