IINA before 1.4.3 contains a user-assisted command execution vulnerability that allows remote attackers to execute arbitrary commands by supplying malicious mpv_-prefixed query parameters through the iina://open custom URL scheme handler. Attackers can deliver a crafted URL via a browser that passes unvalidated mpv_options/input-commands parameters into the mpv runtime, causing arbitrary command execution as the current macOS user upon approval of the browser protocol prompt without requiring a valid media file.