Right click on your Opera shortcut and click on properties, which opens a box. Under the tab marked shortcut you'll see a box marked target, with a path indicated. Add to that path, after a space, -show-component-extension-options. Then click on apply and close the box. Then open Opera and go to extensions.
It took me a couple of tries to get this but now I see that I have no less than 14 hidden extensions, most of which I know nothing about. But I do know I don't need AliExpress or Google Hangouts. Most of the rest I don't have a clue what they're doing there. I have to agree with those who said this is a troubling issue. I don't like having a lot of stuff installed by a program without my knowledge.