How do I uninstall plugins?

Safari has recently started asking me if I want to let whatever website access my Sharepoint plugin with all kinds of websites, or something to that effect. It also says something about not having the highest level of security. I don't know exactly what that plug in does and I don't think I want share information. I also don't know when that plug in got installed. So how do I get rid of it? I know you can go to help and see installed plugins, but it is just a list and I can't see a delete button anywhere. I see some things that I remember allowing to be installed, and some I did not. I also know you can go to preferences and see the added extensions. I only have four. I did add them all. And I know that I can activate, inactivate, or remove them from this screen. However, the plugins don't show up here.

Running Safari 9.0.2 on OS 10.9.5. I know its an older OS, but after reading some upgrade issues with iPhoto, I didn't upgrade. The only thing irreplaceable on the computer are my photos and albums.