Java deserialization in HttpInvokerServiceExporter / RemoteInvocationSerializingExporter
(spring-web remoting). Upstream never code-fixed this on any line: the classes were
deprecated in 5.3.0 and removed in 6.0.0, so there is no fix commit to backport.
Replicating the 6.0 removal would break the API this drop-in build must keep, so the
classes ship unchanged, as in the 5.3.32 and 5.3.39 specs (which record this as a comment).