In open-webui version 0.3.8, the endpoint `/models/upload` is vulnerable to arbitrary file write due to improper handling of user-supplied filenames. The vulnerability arises from the usage of `file_path = f"{UPLOAD_DIR}/{file.filename}"` without proper input validation or sanitization. An attacker can exploit this by manipulating the `file.filename` parameter to include directory traversal sequences, causing the resulting `file_path` to escape the intended `UPLOAD_DIR` and potentially overwrite arbitrary files on the system. This can lead to unauthorized modifications of system binaries, configuration files, or sensitive data, potentially enabling remote command execution.

Open WebUI Allows Arbitrary File Write via the `/models/upload` Endpoint