I'm not sure why you would get a warning while installing Ghostery. Can you tell me what the warning said?

You can ask some of your questions about the process behind determining what a "Featured" add-on is to https://forums.mozilla.org/addons/.

Hi Tylerdowner,

Thanks for quick response. I get warning like "Install add-ons only from Authors you trust" with a yellow triangle.

Seems like there is some serious problem ? I am getting similar warning for WOT Safe Surfing also. see attached image. What should I do? is it a problem? or it's normal to get messages like this?

Oh oh, I see now, sorry about the confusion. That warning is Firefox's way of double-checking that you want to install the add-on. It doesn't mater if it is a featured add-on, or a brand new one. Firefox just wants to confirm that YOU requested to install the add-on, not a malicious website. So, if you wanted to install the add-on, go ahead and just click "Install Now". It is just a security feature built into firefox, and has nothing to do with the add-on. So you are safe to continue.

again, apologies for the confusion. Your screenshot cleared it up instantly.