Hey Folks, I am working on a desktop application and as part of that applications install, if we detect that firefox is installed, we want to install an extension we wrote. For the firefox upgrade urls to work in the future we seem to need to install the plugin as a local plugin. Therefore the following does not work: firefox.exe -install-global-extension extension.xpi My question is, what is the correct way to install this plugin as a local extension for the current user? If this is not possible and we have to install our plugin as a global extension as show above, we run in to the following problem. 1. Let's say firefox 3.6 is installed and we install our extension as a global extension, it works fine 2. Now, The user updates to firefox 4, it detects our plugin needs an update to work with firefox 4 3. The firefox update code runs into an error when trying to update the global extension. We get a very generic error saying there was a problem updating the addin. I should also note that for reasons not important to this thread we have to host the extension on our own servers and not as part of mozilla.