Open WebUI Allows Arbitrary File Write via the `download_model` Endpoint

In version 0.3.8 of open-webui/open-webui, an arbitrary file write vulnerability exists in the download_model endpoint. When deployed on Windows, the application improperly handles file paths, allowing an attacker to manipulate the file path to write files to arbitrary locations on the server's filesystem. This can result in overwriting critical system or application files, causing denial of service, or potentially achieving remote code execution (RCE). RCE can allow an attacker to execute malicious code with the privileges of the user running the application, leading to a full system compromise.