Description:
from Qt Project Security Advisory [0]
"QXmlSimpleReader in Qt versions prior to 5.2 supports expansion of internal
entities in XML documents without placing restrictions to ensure the document
does not cause excessive memory usage. If an application using this API
processes untrusted data then the application may use unexpected amounts of
memory if a malicious document is processed."

Patch :
for qt4 : [1]
for qt5 5.1 : [2]

Ressources :
[0] http://lists.qt-project.org/pipermail/announce/2013-December/000036.html
[1] https://codereview.qt-project.org/#change,71010
[2] https://codereview.qt-project.org/#change,71368