Speaking as engineer.. the Firefox folks don't really get it. You can't just break what sites like StackOverflow and Wikipedia have been doing for years (and in some cases decades) and then say "you were doing the wrong thing." Some version of FPS will ship in browsers, probably in the next 2 years.
Quoting Apple's position directly "[...] Given these issues, I don’t think we’d implement the proposal in its current state. That said, we’re very interested in this area, and indeed, John Wilander [Safari lead] proposed a form of this idea before Mike West’s [Google] later re-proposal. If these issues were addressed in a satisfactory way, I think we’d be very interested. [...]"
Also it was a W3C TAG review. The W3C and IETF are different organizations.
No, they allowed an origin to list other origins whose cookies would be sent back to the serving origin correctly even if they were iframes loaded in the parent origin DOM.
I.e. this is the expected behavior for iframes until Safari decided that there was such a thing as "third party" origins whose web semantics could be broken in their war against advertising.
Google is trying to (partially) restore the expected behavior of iframes so that named origins get their own cookies sent to them, which is how things worked for the first two decades of the web.
Because I can't comment on an RFC I haven't seen, and a quick google search of my own based on your comment turns up nada.
That said - I'm fully aware of the downsides of this approach, but I want my browser to be (to put it crudely) MY FUCKING USER AGENT. I want to be able to allow sharing by default in most cases, and I want a little dropdown menu that shows me the domains a site has listed as friendly/same-entity, and I want a checkbox I can uncheck for each of them.
Then I want an extension API to allow someone else to do the unchecking for me, based on whether the domain is highly correlated with tracking (Google analytics, Segment, Heap, Braze, etc)
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The way I see it, the road to hell is paved with good intentions. If the web was developed in our current climate of security/privacy focus, how likely is it that even a fucking <a href=[3rd party]> would be allowed? Because I see us driving to a spot where this verboten. Which also happens to be the final nail in the coffin for any sort of real open platform.
Welcome to the world where the web is literally subdomains of facebook/google. What a fucking trash place to be.