slixmpp version before commit 7cd73b594e8122dddf847953fcfc85ab4d316416
contains an incorrect Access Control vulnerability in XEP-0223 plugin
(Persistent Storage of Private Data via PubSub) options profile, used
for the configuration of default access model that can result in
all of the contacts of the victim can see private data having been
published to a PEP node. This attack appears to be exploitable
if the user of this library publishes any private data on PEP,
the node isn't configured to be private. This vulnerability appears
to have been fixed in commit 7cd73b594e8122dddf847953fcfc85ab4d316416
which is included in slixmpp 1.4.2.