It was discovered that XStream, a Java library to serialize objects to
XML and back again, was susceptible to XML External Entity attacks.
For the stable distribution (jessie), this problem has been fixed in
version 1.4.7-2+deb8u1.
For the testing distribution (stretch), this problem has been fixed
in version 1.4.9-1.
For the unstable distribution (sid), this problem has been fixed in
version 1.4.9-1.
We recommend that you upgrade your libxstream-java packages.