(In reply to Grassboy Wu from comment #8)
Can you please add this pref back at least in Firefox Developer Edition?
I don't think so.
and they totally know about all the risks.
I am skeptical about this just for you - I work on the browser and filed this ticket and wouldn't claim that I would fully grok the risk. But even if I were to accept your claim, the people finding this pref copy-pasted around the internet aren't going to understand what they just did in about:config.
Take myself as an example, I often include library (written by myself or 3rd library) dynamically in some websites.
It can improve user experience of those websites when I use them. Even if i am not the owner of those websites.
This should work with webextensions. If you can't get it to work, file a bug with specifics that blocks bug 1267027, and we can fix that.
"Open" is the spirit of Firefox. (I still hope so)
Just like that you cannot forbid people to purchase knife just because they may use it to hurt people.
Indeed, but we don't offer it on a platter to people who intend to do us harm. At-runtime flippable preferences that reduce the security protections that the user rightly assumes in the browser are a bad idea in today's world. Everything that erodes the sandboxing and origin separation we build up around websites is a risk. People who need this feature are technical enough to use an extension for it.