Yes, it does. The DHCP option will tell your _OS_ about the PAC file, but the browser won't ask the OS for that information unless the "Use system proxy settings" option (which is the default) is selected. The choices in this dialog map to the preference values I describe in https://news.ycombinator.com/item?id=12175050 as follows:
"No Proxy": 0
"Auto-detect proxy settings for this network": 4
"Use system proxy settings": 5
"Manual proxy configuration": 1
"Automatic proxy configuration URL": 2
If I set Firefox to use system proxy, I suppose it won't be affected by WPAD unless the OS does?
Does anyone know if it's possible to force unpatched libproxy on Linux to not use WPAD? Also, does network-manager use libproxy if I don't have libproxy1-plugin-networkmanager installed?
Menu > Preferences > Advanced > Network > Settings… > No Proxy.
Very simple and easily discoverable setting.
Google Chrome uses your OS's settings for proxy, though, so you can't easily turn it off in most cases, but you can go toSettings (scroll down a page) > Advanced Settings > Network > Configure System Proxy Settings
(that redirects you to the system settings for proxies, usually).