This is a security exception caused by improper Flash plug-in behavior. A Flash security update between version Flash 188.8.131.52 and 184.108.40.206 changed the behavior of the cross-domain security policy file. One of these changes limits arbitrary headers to be sent from a remote domain unless you specify a security policy to do so.
Resolving The Problem
This problem is a result of an uncaught security exception caused by changes in the Flash plug-in. There is no work around at this time and the error should be ignored.
15 June 2018