Hello, I am having an issue with Firefox on Mac not using the system proxy settings. It incessantly prompts for proxy credentials. I have tried resetting/refreshing Firefox. I have tried other "solutions" such as setting network.automatic-ntlm-auth.allow-proxies and network.negotiate-auth.allow-proxies to false; signon.autologin.proxy to true; network.proxy.share_proxy_settings to false. I have tried different formats of username in the prompt (username, domain\username, username@domain). I'm not fat fingering my password. The domain account I'm trying to authenticate with is not locked out. I have tried all the proxy settings (no proxy, auto-detect, use system settings, manual). I have tried reinstalling. Nothing I have tried works. My version of Firefox is 55.0.3. Mac version is Sierra. I know Firefox is the problem because other applications work. Chrome has one authentication popup on launch, which is fine (I don't think Chrome v61 is Keychain aware). Other applications that access the internet do not have this issue; they are reading from the system settings (Keychain) just fine. Does anybody else have this issue? What can I do that I haven't tried yet? Is there a way to make Firefox Keychain aware (even though proxy setting is telling it to use system settings)? Thanks, Craig