Microsoft has fixed the distribution scope of a toolbar update that, without the user's knowledge, installed an add-on in Internet Explorer and an extension in Firefox called Search Helper Extension. Microsoft told us that the new update is actually the same as the old one; the only difference is the distribution settings. In other words, the update will no longer be distributed to toolbars that it shouldn't be added to. End users won't see the tweak, Microsoft told Ars, and also offered an explanation on what the mystery add-on actually does.

The Search Enhancement Pack is a shared component used by the Windows Live Toolbar, MSN Toolbar, and Bing Bar. This component enables toolbar search functionality, like the toolbar search suggestions drop down. It is not the toolbar. It is a component used by the toolbars. Unfortunately, we discovered a bug in the latest update that was installing the Firefox extension for users with the Windows Live Toolbar and MSN Toolbar (specifically people who have not upgraded to the latest version of the Bing Bar). We fixed the update so that going forward folks who still have only the older Windows Live Toolbar or MSN Toolbar will not see this behavior anymore. The extension in Firefox will be update[d] for users who have the Bing Bar or the latest version of MSN Toolbar (version 4.0), since both are available for both IE and FF. We apologize for the inconvenience.

We pointed out to Microsoft that this doesn't solve the problem for all those users who already installed the update. After all, while many Windows Update releases can be uninstalled, this particular one does not show up in Control Panel => Programs and Features => Installed Updates. Furthermore, the Uninstall button for the extension is greyed out in Firefox. Internet Explorer, meanwhile, does not have uninstall options for add-ons: only Enable and Disable buttons are present.

Microsoft gave us the following instructions to remove the extension:

Close all running instances of Firefox. Open Windows Explorer. If you have 32 bit Windows, navigate to C:Program FilesMicrosoftSearch Enhancement PackSearch Helperfirefoxextension If you have 64 bit Windows, navigate to C:Program Files (x86)MicrosoftSearch Enhancement PackSearch Helperfirefoxextension Delete the folder named "SearchHelperExtension" Start Firefox. Go to Tools > Add-ons and verify that Search Helper Extension is gone.

We tested these instructions on the same two systems we first noticed the issue on, and we found that the extension was indeed removed. We noted in our original report that the firefoxextension folder was responsible for, well, the Firefox extension and that the SEPsearchhelperie.dll in the Search Helper folder is responsible for the IE add-on, but it turns out that deleting it does not kill the add-on completely. Microsoft told us it would not provide instructions on removing the IE add-on because "IE users shouldn’t try to uninstall this if they are keeping Windows Live Tool Bar or the old MSN Tool Bar, or else the search functionality will be broken."

Unfortunately, these removal instructions only remove the extension in question, and while this is what most users were complaining about, the actual update remains installed. Thus, in order to test that the update is being offered to the correct users again, we took a third machine, installed the Windows Live Toolbar on it, and checked to see if was offered. It was not. If you own a machine that does not have the Bing Bar or version 4 of the MSN Toolbar and you're seeing this update, please let us know in the comments below.