The QSharedMemory class in Qt 5.0.0, 4.8.x before 4.8.5, 4.7.x before 4.7.6, and other versions including 4.4.0 uses weak permissions (world-readable and world-writable) for shared memory segments, which allows local users to read sensitive information or modify critical program data, as demonstrated by reading a pixmap being sent to an X server.
https://bugzilla.redhat.com/show_bug.cgi?id=907425
http://rhn.redhat.com/errata/RHSA-2013-0669.html
http://lists.qt-project.org/pipermail/announce/2013-February/000023.html
http://lists.opensuse.org/opensuse-updates/2013-03/msg00019.html
http://lists.opensuse.org/opensuse-updates/2013-03/msg00015.html
http://lists.opensuse.org/opensuse-updates/2013-03/msg00014.html