/etc/dhcp/dhclient-exit-hooks.d/wpad-proxy-update is in debian-edu-config 1.702.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | # Update proxy settings using wpad-url DHCP option or
# http://wpad/wpad.dat when a DHCP update arrives
update_proxy_from_wpad() {
    # Not comparing the old and new URL, as the URL might be the same
    # but the content of the WPAD file changed.  If the option is not
    # set and no wpad file is available from http://wpad/wpad.dat ,
    # the use of a proxy should be disabled.
    /usr/share/debian-edu-config/tools/update-proxy-from-wpad "$new_wpad_url"
}
if [ -r /etc/debian-edu/config ] ; then
    . /etc/debian-edu/config
fi
if [ false = "$DHCP_WPAD_PROXY_UPDATE" ] ; then
    exit 0
fi
case $reason in
    BOUND|RENEW|REBIND|REBOOT)
	update_proxy_from_wpad
	;;
    EXPIRE|FAIL|RELEASE|STOP)
	;;
esac
 |