yt-dlp is a youtube-dl fork with additional features and fixes. yt-dlp allows
the user to provide shell command lines to be executed at various stages in its
download steps through the `--exec` flag. This flag allows output template
expansion in its argument, so that metadata values may be used in the shell
commands. The metadata fields can be combined with the `%q` conversion, which is
intended to quote/escape these values so they can be safely passed to the shell.
However, the escaping used for `cmd` (the shell used by Python's `subprocess` on
Windows) does not properly escape special characters, which can allow for remote
code execution if `--exec` is used directly with maliciously crafted remote
data. This vulnerability only impacts `yt-dlp` on Windows, and the vulnerability
is present regardless of whether `yt-dlp` is run from `cmd` or from
`PowerShell`. Support for output template expansion in `--exec`, along with this
vulnerable behavior, was added to `yt-dlp` in version 2021.04.11. yt-dlp version
2023.09.24 fixes this issue by properly escaping each special character. `\n`
will be replaced by `\r` as no way of escaping it has been found. It is
recommended to upgrade yt-dlp to version 2023.09.24 as soon as possible. Also,
always be careful when using --exec, because while this specific vulnerability
has been patched, using unvalidated input in shell commands is inherently
dangerous. For Windows users who are not able to upgrade: 1. Avoid using any
output template expansion in --exec other than {} (filepath). 2. If expansion in
--exec is needed, verify the fields you are using do not contain ", | or &. 3.
Instead of using --exec, write the info json and load the fields from it
instead.


References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2023-40581