Saxy's XML encoder writes the target and the content of a processing instruction into the output document verbatim, without validation or escaping. The encoder builds the construct by concatenating both fields between , so neither field is checked against the constraints the XML specification places on it. Because ?> terminates a processing instruction, a target or content value containing that sequence closes the construct at a position the attacker chooses. Everything the attacker writes after it is emitted as ordinary markup at document level, which allows arbitrary elements, attributes, and further processing instructions to be injected into the serialized document. Appending a matching
CWE-91