XWiki Admin Tools Application Run Shell Command allows CSRF RCE attacks

Summary

The XWiki Admin Tools Application provides tools to help the administration of XWiki. Starting in version 4.4 and prior to version 4.5.1, a cross site request forgery vulnerability in the admin tool for executing shell commands on the server allows an attacker to execute arbitrary shell commands by tricking an admin into loading the URL with the shell command. A very simple possibility for an attack are comments. When the attacker can leave a comment on any page in the wiki it is sufficient to include an image with an URL like `/xwiki/bin/view/Admin/RunShellCommand?command=touch%20/tmp/attacked` in the comment. When an admin views the comment, the file `/tmp/attacked` will be created on the server. The output of the command is also vulnerable to XWiki syntax injection which offers a simple way to execute Groovy in the context of the XWiki installation and thus an even easier way to compromise the integrity and confidentiality of the whole XWiki installation. This has been patched by adding a form token check in version 4.5.1 of the admin tools. Some workarounds are available. The patch can be applied manually to the affected wiki pages. Alternatively, the document `Admin.RunShellCommand` can also be deleted if the possibility to run shell commands isn't needed.