I have one app that will be processing real-time updates for subscriptions of multiple Facebook applications. In the verify signature step, I need to know for which Facebook application Facebook is giving me updates (so I can use the correct app secret). I haven't seen a sample request that provides this information but I could be missing it. Is there a way to know which app the subscriptions are for (without iterating though my known apps and trying each secret until one works)?
One thought I had was to subscribe to Facebook and providing a callback URL that has the App ID in the path so I could parse it that way.