yt-dlp's --exec option is vulnerable to arbitrary command injection when unsafe string formatting conversions are used in the command template. This allows an attacker to execute arbitrary shell commands via maliciously crafted video metadata. The vulnerability affects users who use unsafe conversions like %()s in --exec templates. yt-dlp 2026.06.09 fixes this by restricting allowed conversions to safe ones and limiting characters in templates. Users can mitigate by upgrading or avoiding unsafe conversions or the --exec option altogether.