An unrestricted file upload vulnerability exists in BuilderEngine 3.5.0 via the integration of the elFinder 2.0 file manager and its use of the jQuery File Upload plugin. The plugin fails to properly validate or restrict file types or locations during upload operations, allowing an attacker to upload a malicious .php file and subsequently execute arbitrary PHP code on the server under the context of the web server process. While the root vulnerability lies within the jQuery File Upload component, BuilderEngine’s improper integration and lack of access controls expose this functionality to unauthenticated users, resulting in full remote code execution.