Can users accidentally share variables set in the Request scope?
No. The Request scope exists on a per http request basis, i.e. the variables in the Request scope only exist while ColdFusion is completing that single request. They die as soon as ColdFusion has finished processing the request. If your server is set up to process 5 maximum simultanious connections, then, in theory, there could be 5 sets of Request variables in server memory. Each set is tied to a particular http request and cannot exist in another page request unless you copy them into another scope.