M-Link R14.6 before R14.6v14 and R15.1 before R15.1v10 does not verify that a request was made for an XMPP Server Dialback response, which allows remote XMPP servers to spoof domains via responses for domains that were not asserted.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.