The uP_args parameter allows to pass parameters to channels, used with uP_fname. When the uP_args contains a '&', the parameter is not correctly passed to the channel.

Example: if one wants to pass the parameter "xxx&yyy" to a channel he will use a URL such as http://hostname/uPortal/Login?uP_fname=channel&uP_args=xxx%26yyy. The LoginServlet reads the uP_args parameter (xxx%26yyy) and redirects to a new URL build by simply concatenating the value to the URL, which gives somthing like http://hostname/uPortal/tag.idempotent.render.userLayoutRootNode.uP?uP_args=xxx&yyy&uP_fname=channel. It is easy to see that the value of uP_args is now xxx instead of xxx&yyy.