Unrestricted File Upload exists in BigTree CMS before 4.2.17: if an attacker uploads an 'xxx.php[space]' file, they could bypass a safety check and execute any code.
https://github.com/bigtreecms/BigTree-CMS/issues/276
https://github.com/bigtreecms/BigTree-CMS/commit/8cf4212ea40e1b843e1aecf4b24681b0964ec04c