1. A method comprising: (a) maintaining, by a device intermediary to a client and a server, statistical data about messages of a user session that are rejected based on a rejection rule that rejects messages for having an identified attribute; (b) determining, by the device, from the statistical data the frequency count at which messages of the user session having the identified attribute are rejected; (c) comparing, by the device, the frequency count of the rejected messages within the user session to a threshold; (d) generating, by the device for the user session, responsive to the comparison, an exception rule to the rejection rule, the exception rule allowing messages having the identified attribute to pass; (e) receiving, by the device, via the user session a message having the identified attribute; and (f) allowing, by the device, the message of the user session to pass between the client and the server based on the exception rule that allows messages having the identified attribute to pass.