This attack could pose a serious security threat. You should take immediate action to stop any damage or prevent further damage from happening.
This signature detects attempts of leveraging a vulnerability in XmlImportExport plugin for MantisBT which could lead to execute arbitrary PHP code.
MantisBT is a web-based bug management application implemented in PHP.
XmlImportExport plugin for MantisBT is prone to an arbitrary PHP code-execution vulnerability because it fails to properly validate user-supplied input submitted to the 'description' field of the 'ImportXml.php' script. Specifically, this issue affects the 'preg_replace()' function.
An attacker can exploit this issue to execute arbitrary PHP code within the context of the web server.