How to create an auto updater for browser extensions/addons?

I need to create an auto-updater on clients computer that will automatically update a particular addon on Internet Explorer, Firefox, ... Of course user previously agrees that there will be automatic updates on his computer.

Do you guys have any idea where I could start to do this ?

I started thinking about running a process on the client side that with ask our server every couple of hours if there is a new version and then do the necessary update on the client side.

The idea is to update our addon on multiple browsers without prompting the user of a new version.

Is there any tools that you could recommend ? Thank you for the help.

Edit: I can use Firefox and Chrome 开发者_Go百科'updateURL' in the manifest. But how do I automatically update a BHO (IE extension), and a Safari extension ?

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Firefox and Chrome have a built-in extension updater, an extension shouldn't bring its own. The updater works by periodically checking a particular URL for information on the current extension version. Firefox documentation: https://developer.mozilla.org/en/Install_Manifests#updateURL. Chrome documentation: http://code.google.com/chrome/extensions/autoupdate.html.