That plugin is the responsibility of VMWare, as with all addons for Firefox. They need to update that plugin for their users.

One change between Firefox 3.5.x versions and Firefox 3.6 is that Plugins can't be "dropped" into the \Program Files\Mozilla\Firefox\plugins\ folder by the plugins installer, as was allowed previously. The proper method of installing a "plugin" in 3.6 and later versions, is through the Windows Registry. (How to do that is above my knowledge level, but the instructions for developers is in the Mozilla Developers Center website.)

(That was the first step Mozilla took to prevent un-intended or un-authorized installation of plugins the user didn't specifically allow. Firefox 4.0 has other modifications to prevent that from happening, by not providing a \plugins\ folder at all, with the default installation.)

If you copy the plugin DLL file from the 3.5 \plugins\ folder to the 3.6 \plugins\ folder yourself, that plugin should work properly in Firefox 3.6 versions.

In the upcoming Firefox 4.0, you should be able to create the \plugins\ folder yourself, and then copy the DLL file into that folder. I said - should - as of 4.0b5 that worked, but might not in later beta version or the actual release, we'll have to see about that. As to whether the API the plugin uses is still in 4.0, that is for the plugin developer to determine by testing their plugin with the 4.0 betas. YMMV

What is the "proper" method of installing a plugin with Firefox 3.6 on linux? Because the VMware console plugin doesn't work on linux either.