Cross-site Scripting in Apache Struts

When the Struts2 debug mode is turned on, under certain conditions an arbitrary script may be executed in the 'Problem Report' screen. Also if JSP files are exposed to be accessed directly it's possible to execute an arbitrary script.

It is generally not advisable to have debug mode switched on outside of the development environment. Debug mode should always be turned off in production setup. Also never expose JSPs files directly and hide them inside WEB-INF folder or define dedicated security constraints to block access to raw JSP files.

Struts >= 2.3.20 is not vulnerable to this attack. We recommend upgrading to Struts 2.3.20 or higher if turning off debug mode is not possible.