Arbitrary File Upload in user_payment_update.php in SourceCodester Client Database Management System 1.0 allows unauthenticated users to upload arbitrary files via the uploaded_file_cancelled field. Due to the absence of proper file extension checks, MIME type validation, and authentication, attackers can upload executable PHP files to a web-accessible directory (/files/). This allows them to execute arbitrary commands remotely by accessing the uploaded script, resulting in full Remote Code Execution (RCE) without authentication.

Arbitrary File Upload in user_payment_update.php in SourceCodester Client Database Management System 1.0 allows unauthenticated users to upload arbitrary files via the uploaded_file_cancelled field. Due to the absence of proper file extension checks, MIME type validation, and authentication, attackers can upload executable PHP files to a web-accessible directory (/files/). This allows them to execute arbitrary commands remotely by accessing the uploaded script, resulting in full Remote Code Execution (RCE) without authentication.