xidown - Argument Injection via Unterminated yt-dlp Command Line Construction

xidown (a yt-dlp/ffmpeg GUI wrapper) builds its yt-dlp command-line invocation (xidown/core/scanner.py and downloader.py) by appending the user-provided or scanned URL as a bare trailing positional argument, with no '--' end-of-options marker and no scheme validation anywhere in the codebase.