Right now it is not possible/practical to communicate across SecurityDomains because you cannot share classes across the domain boundary. Expected Results: I would expect that you could create some way to share a subset of classes across domain boundaries. Comments from flash player bugbase: [aharui 5/14/07] Entered Bug. This is critical post-Moxie to allow Flex to create usable portals. Apollo also feels like this will be a critical topology soon. [ktoley 5/14/07] Sending to QRB [ecostell 5/15/07] Open to Deneb for FP10 assessment [dmeketa 2/28/08] To QRB. This is not really my area. This is much more an issue for the VM team. Marking [KEEP-Bacon] because this is a major feature that has been requested many times. People want the ability to have identical classes be compatible across ApplicationDomains. Security is only a minor aspect of this issue.