Sigma Forms Pro <= 1.4.5 - Unauthenticated Unauthenticated Arbitrary File Upload Leading to Remote Code Execution via Pre-built Template File Upload Field

The Sigma Forms Pro plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 1.4.5 via the handle_form_submission function. This is due to the plugin dynamically granting the unfiltered_upload capability to all users during form submissions and bypassing MIME type validation when allowed_file_types is not configured. This makes it possible for unauthenticated attackers to execute code on the server. Several default pre-built templates including Job Application, Support Ticket, and Wholesale Application have file upload fields with no file type restrictions configured by design, making this vulnerability immediately exploitable upon installation.