fix(yt-dlp): terminate yt-dlp option parsing and validate the link

packages/yt-dlp/src/download.ts

@@ -52,6 +52,10 @@ export function isVideoUrl(value: string): boolean {
  * The container follows the target's extension.
  */
 export async function downloadVideo(url: string, target: string, options: { readonly signal?: AbortSignal } = {}): Promise<void> {
+  const link = url.trim();
+  if (!isVideoUrl(link)) {
+    throw new Error(`Video link ${url} must be an http or https URL`);
+  }
   const container = extname(target).slice(1).toLowerCase();
   if (!["mp4", "mkv", "webm", "mov"].includes(container)) {
     throw new Error(`${target} must end in .mp4, .mkv, .webm or .mov`);
@@ -74,7 +78,9 @@ export async function downloadVideo(url: string, target: string, options: { read
         "--merge-output-format", container,
         "--format-sort", "res:1080,vcodec:h264",
         "--output", join(work, "video.%(ext)s"),
-        url,
+        // Terminate option parsing: a link-shaped argument must never re-enable an option
+        // (--plugin-dirs would run Python code from a caller-named directory).
+        "--", link,
       ], { timeout: 900_000, maxBuffer: 10 * 1024 * 1024, signal: options.signal });
     } catch (cause) {
       if (options.signal?.aborted) throw cause;

packages/yt-dlp/test/download.test.ts

@@ -69,6 +69,7 @@ test("download resolves its locked runtime from an installed package outside the
     assert.match(command, /yt-dlp/u);
     assert.ok(args.includes("--no-remote-components"));
     assert.ok(args.includes("--ignore-config"));
+    assert.equal(args.at(-2), "--", "the link must sit behind the end-of-options separator");
     assert.equal(args.at(-1), "https://example.test/video");
     const output = args[args.indexOf("--output") + 1]!.replace("%(ext)s", "mp4");
     writeFileSync(output, "downloaded bytes");
@@ -83,6 +84,17 @@ test("download resolves its locked runtime from an installed package outside the
   assert.equal(calls, 3);
 });
 
+test("download refuses option-shaped links before touching the environment", async () => {
+  await assert.rejects(
+    downloadVideo("--plugin-dirs=/tmp/evil", join(tmpdir(), "never.mp4")),
+    /http or https URL/u,
+  );
+  await assert.rejects(
+    downloadVideo("file:///etc/passwd", join(tmpdir(), "never.mp4")),
+    /http or https URL/u,
+  );
+});
+
 test("the pinned yt-dlp project belongs to its behavior package", () => {
   const project = fileURLToPath(new URL("../runtime", import.meta.url));
   assert.ok(existsSync(join(project, "pyproject.toml")));