Streamlink has an arbitrary local file read via file:// URI in HLS and DASH
Streamlink's HLS and DASH parsers do not validate the URI scheme of segment entries and other resources. A remote .m3u8 HLS playlist or .mpd DASH manifest can list file:///path/to/file as a segment, and streamlink will read that local file and write its contents to the output stream. Confirmed on streamlink 8.3.0 (latest release at time of report).