at

The issue is apparently lack of queue management support in the command. Meaning that on a multi-user system a bunch of people could schedule tasks at the same time, which could amount to a denial of service attack. Also you don't want commands like that usable by users such as the web server; so by default at denies everyone but root.

However, if you really want to use at for something, send a note to support@Vex.Net. We will enable it for individual users with a use for it.