The XmlImportExport plugin in MantisBT 1.2.17 and earlier allows remote attackers to execute arbitrary PHP code via a crafted (1) description field or (2) issuelink attribute in an XML file, which is not properly handled when executing the preg_replace function with the e modifier.
https://github.com/mantisbt/mantisbt/commit/bed19db9
https://github.com/mantisbt/mantisbt/commit/84017535
https://exchange.xforce.ibmcloud.com/vulnerabilities/98572
http://www.securityfocus.com/bid/70993
http://www.mantisbt.org/bugs/view.php?id=17725
http://www.debian.org/security/2015/dsa-3120