In proxy script, url argument of FindProxyFurURL is missing path and query information.
Even with
network.proxy.autoconfig_url.include_path=true
New WebExtension API is used and web-ext tool for development.
Addon is loaded with web-ext run --pref network.proxy.autoconfig_url.include_path=true
about:config shows “true” for network.proxy.autoconfig_url.include_path as well