yt-dlp is a youtube-dl fork with additional features and fixes. The Generic Extractor in yt-dlp is vulnerable to an attacker setting an arbitrary proxy for a request to an arbitrary url, allowing the attacker to MITM the request made from yt-dlp's HTTP session. This could lead to cookie exfiltration in some cases. Version 2023.11.14 removed the ability to smuggle `http_headers` to the Generic extractor, as well as other extractors that use the same pattern. Users are advised to upgrade. Users unable to upgrade should disable the Ggneric extractor (or only pass trusted sites with trusted content) and ake caution when using `--no-check-certificate`.
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.