I'm trying to set up proxy autoconfiguration in my FireFox 45.0 under Kubuntu 15.10. I'm specifying a path to PAC file in FF's Preferences\Advanced\Settings\"Automatic proxy configuration URL". It works for a few minutes and then stops. When I check this setting again I'm able to see the path in the corresponding field but setting's radiobutton is switched back to "Use system proxy settings".
I suspect there is a system demon that resets my change. What is a correct way to do this in FF under Kubuntu?
It was because of ZenMate extension in my FF. Even I switched it off from browser's toolbar it still interfere with this setting. I bypassed this problem by disabling ZenMate extension in FF settings.