I see more and more of these System Add-ons appearing - see about:support and the Firefox Features section. Investigating all these gets to be a pain but an interesting resource I've found so far is here: http://news.superrune.dk/20170730/686a7 ... cc448.html
The shield thing sounds particularly iffy (extensions.shield-recipe-client.enabled) - https://wiki.mozilla.org/Firefox/Shield/
...and, no, I didn't make that up.mozilla wiki wrote:Shield is a system that addresses user attrition and satisfaction in Firefox by providing a fast and powerful way for Firefox to interact with our users.
Me, I just try and turn off everything I can now because I can no longer be arsed to find out exactly what Mozilla are up to even if it might turn out to be something useful. But then I have a yellow sticker on my forehead that says: LEGACY.
Ben.