I have just filed http://www.igniterealtime.org/issues/browse/JM-1495 though i’m not quite sure about this and there is no a real patch yet to test. But ithink it’s worth looking. Also, Dele (Red5 Flash plugin author) confirms something is wrong in Openfire null bytes handling.
Pity i cant test my SparkWeb on the production server with 3.6.1 till Friday. Testing on a localhost is not sufficient in this case.