yt-dlp is a command-line audio/video downloader. From 2023.09.24 until 2026.06.09, if curl is used as an external downloader for yt-dlp, cookies may be leaked to an unintended host upon HTTP redirect or when the host for download fragments differs from their parent manifest's. At the file download stage, the cookies are passed by yt-dlp to the file downloader via --cookie. However, unless these are loaded from a file, this operation does not activate the cookie engine. As a result, curl will send cookies with requests to domains or paths for which the cookies are not scoped. This vulnerability is fixed in 2026.06.09.