An issue was discovered in CMS Made Simple 2.2.8. It is possible to achieve unauthenticated path traversal in the CGExtensions module (in the file action.setdefaulttemplate.php) with the m1_filename parameter; and through the action.showmessage.php file, it is possible to read arbitrary file content (by using that path traversal with m1_prefname set to cg_errormsg and m1_resettodefault=1).
https://www.cmsmadesimple.org/2019/03/Announcing-CMS-Made-Simple-v2.2.10-Spuzzum
https://newsletter.cmsmadesimple.org/w/89247Qog4jCRCuRinvhsofwg