Disclosed are various embodiments for executing untrusted content in a trusted network through the use of an external proxy server application. An identification of a resource specified by a user is obtained in one or more computing devices. The user is associated with one of a plurality of network sites hosted by the one or more computing devices. The one or more computing devices are within a trusted network that is separated from an untrusted network by a firewall. The resource is obtained from an external proxy server application executed in the untrusted network. One or more network pages are generated for the one of the network sites based at least in part on the resource.