Firefox won't go "offline" when using a proxy on localhost

[Sadako]

I'm using firefox 52.6 with privoxy, and have only just noticed that it can still connect to non-https sites just fine even when "work offline" is enabled.

https sites show the "Offline mode" warning as expected, as I'm only sending http traffic to privoxy, not ssl.

If I change privoxy to listen on my lan ip address rather that 127.0.0.1 (and change firefox to connect to that) offline mode works as expected, i.e. can't connect to anything.

I've been using privoxy with firefox for years, and have used offline mode a lot, but have only just noticed this now, somehow...

This seems like a fairly serious firefox bug, but googling hasn't turned up anything on it.

Can anyone else confirm this?
_________________
"You have to invite me in"

[gerdesj]

[Hu]

Firefox 52 is the current ESR, and is mandatory for anyone who wants their extensions to work with minimum hassle. Upgrading to current non-ESR means using a build that only supports "WebExtensions", a crippled new standard that lacks support for a variety of popular extensions. Some of those extensions have been, or will soon be, ported to the new standard. Some have been abandoned by their authors due to frustration with changing goal posts.