We have many computers with Windows8 now but 2008R2 server which doesn't like anything newer than Internet Explorer 9.
Setting proxy for IE8 and IE9 was simple with Interet Explorer .adm files.
You can use Internet Explorer Administration Kit (IEAK) for deploying customized Internet Explorer and it works, but for me works only if you deploy full installation with only changed proxy settings. It was very weird to me, so I searched another way.
Finally, my thoughts were directed to Windows registry. Everyone nows that if something is hidden from your eyes you can set it through the registry.
And this is it, keys that set your path for proxy .pac file!
For adding proxy address:
reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings" /v AutoConfigURL /t REG_SZ /d "http://yourproxyaddress.here/proxy.pac" /f
For removing proxy address:
reg del "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings" /v AutoConfigURL /t REG_SZ /d "" /f
I've set gpo for that:
As you see I've used Preferences settings to add new registry settings
Settings in the add registry you can see below: