警报功能被添加到沙箱中：

80         // add predefined functions to pac
81         this._sandBox.importFunction(myIpAddress);
82         this._sandBox.importFunction(dnsResolve);
83         this._sandBox.importFunction(proxyAlert,"alert");

并且映射函数调用转储到错误控制台：

108 function proxyAlert(msg) {
109     msg = XPCSafeJSObjectWrapper(msg);
110     try {
111         // It would appear that the console service is threadsafe.
112         var cns = Components.classes["@mozilla.org/consoleservice;1"]
113                             .getService(Components.interfaces.nsIConsoleService);
114         cns.logStringMessage("PAC-alert: "+msg);
115     } catch (e) {
116         dump("PAC: proxyAlert ERROR: "+e+"\n");
117     }