From 26916b7bddbcc2ef782a59bd31c79801ff5258b4 Mon Sep 17 00:00:00 2001
From: James Russo <james.russo@heygen.com>
Date: Wed, 9 Sep 2026 08:50:48 -0400
Subject: [PATCH] fix(cli): validate captured Lottie archives and previews
 (#3811)

* fix(cli): validate captured Lottie archives and previews

* fix(cli): bound Lottie discovery before buffering

* fix(cli): bound Lottie discovery lifecycle and archive paths

* fix(cli): retain highest-priority Lottie candidates
---
 packages/cli/src/capture/index.ts             |  48 ++-----
 .../capture/lottieArchiveEntryLimit.test.ts   |  19 +++
 .../cli/src/capture/lottieArchivePreflight.ts |  59 +++++++++
 .../cli/src/capture/lottieDiscovery.test.ts   | 122 ++++++++++++++++++
 packages/cli/src/capture/lottieDiscovery.ts   | 105 +++++++++++++++
 .../src/capture/lottiePreviewRequests.test.ts |  23 ++++
 .../cli/src/capture/lottiePreviewRequests.ts  |  24 ++++
 .../cli/src/capture/lottieValidation.test.ts  |  66 ++++++++++
 packages/cli/src/capture/lottieValidation.ts  | 107 +++++++++++++++
 packages/cli/src/capture/mediaCapture.test.ts |  35 ++++-
 packages/cli/src/capture/mediaCapture.ts      |  63 ++++-----
 11 files changed, 596 insertions(+), 75 deletions(-)
 create mode 100644 packages/cli/src/capture/lottieArchiveEntryLimit.test.ts
 create mode 100644 packages/cli/src/capture/lottieArchivePreflight.ts
 create mode 100644 packages/cli/src/capture/lottieDiscovery.test.ts
 create mode 100644 packages/cli/src/capture/lottieDiscovery.ts
 create mode 100644 packages/cli/src/capture/lottiePreviewRequests.test.ts
 create mode 100644 packages/cli/src/capture/lottiePreviewRequests.ts
 create mode 100644 packages/cli/src/capture/lottieValidation.test.ts
 create mode 100644 packages/cli/src/capture/lottieValidation.ts

diff --git a/packages/cli/src/capture/index.ts b/packages/cli/src/capture/index.ts
index b29285de37..e7dbb3076d 100644
--- a/packages/cli/src/capture/index.ts
+++ b/packages/cli/src/capture/index.ts
@@ -1,3 +1,4 @@
+import { LottieDiscovery } from "./lottieDiscovery.js";
 import { createCaptureDownloadBudget } from "./readBoundedResponse.js";
 /**
  * Website capture orchestrator.
@@ -84,6 +85,7 @@ export async function captureWebsite(
     onPhase,
   } = opts;
 
+  const downloadByteBudget = createCaptureDownloadBudget();
   const warnings: string[] = [];
   const progress = (stage: string, detail?: string) => {
     onProgress?.(stage, detail);
@@ -204,51 +206,20 @@ export async function captureWebsite(
 
     // Intercept network responses to detect Lottie JSON files
     const discoveredLotties: DiscoveredLottie[] = [];
+    const lottieDiscovery = new LottieDiscovery();
     // Layer 1 (passive video discovery): every direct-video URL the page fetches
     // over the whole session (load / scroll / carousel rotation), independent of
     // whether a <video> for it exists at snapshot time. captureVideoManifest
     // downloads these (guarded) and merges them into the manifest.
     const discoveredVideoUrls = new Set<string>();
     // fallow-ignore-next-line complexity
-    page1.on("response", async (response) => {
+    page1.on("response", (response) => {
       try {
         const responseUrl = response.url();
         if (/\.(mp4|webm|mov|m4v)(\?|#|$)/i.test(responseUrl)) {
           discoveredVideoUrls.add(responseUrl);
         }
-        const contentType = response.headers()["content-type"] || "";
-        const isJsonUrl = responseUrl.endsWith(".json");
-        const isLottieUrl = responseUrl.endsWith(".lottie");
-        const isJson =
-          contentType.includes("application/json") || contentType.includes("text/plain");
-
-        if (isLottieUrl) {
-          discoveredLotties.push({ url: responseUrl });
-          return;
-        }
-
-        if (isJsonUrl || isJson) {
-          // Check Content-Length before downloading to avoid OOM on huge responses
-          const cl = parseInt(response.headers()["content-length"] || "0", 10);
-          if (cl > 5_000_000) return;
-          const buffer = await response.buffer();
-          if (buffer.length < 100 || buffer.length > 5_000_000) return; // Skip tiny or huge
-          const text = buffer.toString("utf-8");
-          const json = JSON.parse(text);
-          // Validate Lottie structure: must have version, in/out points, layers, dimensions, framerate
-          if (
-            json &&
-            typeof json === "object" &&
-            ["v", "ip", "op", "layers", "w", "h", "fr"].every((k: string) => k in json)
-          ) {
-            discoveredLotties.push({
-              url: responseUrl,
-              data: json,
-              dimensions: { w: json.w, h: json.h },
-              frameRate: json.fr,
-            });
-          }
-        }
+        lottieDiscovery.collect(response);
       } catch {
         /* not JSON or parse error — skip */
       }
@@ -382,10 +353,16 @@ export async function captureWebsite(
       /* DOM scan failed — non-critical */
     }
 
+    for (const found of await lottieDiscovery.run(downloadByteBudget, remainingMs)) {
+      const existing = discoveredLotties.findIndex((item) => item.url === found.url);
+      if (existing < 0) discoveredLotties.push(found);
+      else discoveredLotties[existing] = found;
+    }
+
     if (discoveredLotties.length > 0 && remainingMs() > 0) {
       const lottieDir = join(outputDir, "assets", "lottie");
       mkdirSync(lottieDir, { recursive: true });
-      const lottieBudget = { remainingMs };
+      const lottieBudget = { remainingMs, byteBudget: downloadByteBudget };
       const savedCount = await saveLottieAnimations(discoveredLotties, lottieDir, lottieBudget);
       // Generate manifest + preview thumbnails so the agent can SEE what each animation is
       if (savedCount > 0 && remainingMs() > 0) {
@@ -609,7 +586,6 @@ export async function captureWebsite(
     // `budget-exhausted` for every one of them replaces a warning string that could only ever
     // say "some". A zero budget means it breaks on the first url, so this costs no network.
     phase("fonts", "started");
-    const downloadByteBudget = createCaptureDownloadBudget();
     const fontPass = await downloadAndRewriteFonts(extracted.headHtml, outputDir, {
       remainingMs,
       byteBudget: downloadByteBudget,
diff --git a/packages/cli/src/capture/lottieArchiveEntryLimit.test.ts b/packages/cli/src/capture/lottieArchiveEntryLimit.test.ts
new file mode 100644
index 0000000000..57ea741b30
--- /dev/null
+++ b/packages/cli/src/capture/lottieArchiveEntryLimit.test.ts
@@ -0,0 +1,19 @@
+import { describe, expect, it, vi } from "vitest";
+import { readLottieArchive } from "./lottieValidation.js";
+
+const getEntries = vi.hoisted(() => vi.fn(() => []));
+vi.mock("adm-zip", () => ({
+  default: class {
+    getEntryCount() {
+      return 1000;
+    }
+    getEntries = getEntries;
+  },
+}));
+
+describe("Lottie archive entry allocation", () => {
+  it("rejects the EOCD count without materializing entries", () => {
+    expect(readLottieArchive(Buffer.from("archive metadata supplied by test"))).toBeNull();
+    expect(getEntries).not.toHaveBeenCalled();
+  });
+});
diff --git a/packages/cli/src/capture/lottieArchivePreflight.ts b/packages/cli/src/capture/lottieArchivePreflight.ts
new file mode 100644
index 0000000000..e4c4ec2ea1
--- /dev/null
+++ b/packages/cli/src/capture/lottieArchivePreflight.ts
@@ -0,0 +1,59 @@
+/** Bound raw central-directory names before adm-zip synthesizes their parent folders. */
+export function preflightLottieArchive(bytes: Buffer): boolean {
+  const end = findDirectoryEnd(bytes);
+  if (end < 0) return false;
+  if (!unambiguousFooter(bytes, end)) return false;
+  const count = bytes.readUInt16LE(end + 10);
+  if (count > 256 || bytes.readUInt16LE(end + 8) !== count) return false;
+  if (bytes.readUInt32LE(end + 4) !== 0) return false; // no multi-disk archives
+  let offset = bytes.readUInt32LE(end + 16);
+  const directoryEnd = offset + bytes.readUInt32LE(end + 12);
+  if (directoryEnd > end) return false;
+  for (let i = 0; i < count; i++) {
+    const next = nextBoundedEntry(bytes, offset, directoryEnd);
+    if (next === null) return false;
+    offset = next;
+  }
+  return offset === directoryEnd;
+}
+
+function unambiguousFooter(bytes: Buffer, end: number): boolean {
+  const signature = Buffer.from([0x50, 0x4b, 0x05, 0x06]);
+  if (bytes.lastIndexOf(signature) !== end) return false;
+  // adm-zip scans just before EOCD for alternate/ZIP64 records. This bounded
+  // archive format does not need those; do not let it select another directory.
+  const preceding = bytes.subarray(Math.max(0, end - 76), end);
+  return ![
+    signature,
+    Buffer.from([0x50, 0x4b, 0x06, 0x06]),
+    Buffer.from([0x50, 0x4b, 0x06, 0x07]),
+  ].some((marker) => preceding.includes(marker));
+}
+
+function findDirectoryEnd(bytes: Buffer): number {
+  for (let at = bytes.length - 22; at >= Math.max(0, bytes.length - 65557); at--) {
+    if (
+      bytes.readUInt32LE(at) === 0x06054b50 &&
+      at + 22 + bytes.readUInt16LE(at + 20) === bytes.length
+    )
+      return at;
+  }
+  return -1;
+}
+
+function nextBoundedEntry(bytes: Buffer, offset: number, end: number): number | null {
+  if (offset + 46 > end || bytes.readUInt32LE(offset) !== 0x02014b50) return null;
+  const length = bytes.readUInt16LE(offset + 28);
+  const next =
+    offset + 46 + length + bytes.readUInt16LE(offset + 30) + bytes.readUInt16LE(offset + 32);
+  if (length > 512 || next > end) return null;
+  const name = bytes.toString("utf8", offset + 46, offset + 46 + length);
+  return safeLottieArchivePath(name) ? next : null;
+}
+
+export function safeLottieArchivePath(path: string): boolean {
+  if (path.length > 512 || path.split("/").length > 16) return false;
+  if (path.startsWith("/") || /[\\:]/.test(path)) return false;
+  if (Array.from(path).some((char) => char.charCodeAt(0) < 32)) return false;
+  return path.split("/").every((segment) => segment !== ".." && segment !== ".");
+}
diff --git a/packages/cli/src/capture/lottieDiscovery.test.ts b/packages/cli/src/capture/lottieDiscovery.test.ts
new file mode 100644
index 0000000000..c2d71478ed
--- /dev/null
+++ b/packages/cli/src/capture/lottieDiscovery.test.ts
@@ -0,0 +1,122 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { discoverLottieResponse, LottieDiscovery } from "./lottieDiscovery.js";
+
+describe("bounded Lottie discovery", () => {
+  it("awaits delayed candidates and ignores response events after its save boundary", async () => {
+    const discovery = new LottieDiscovery();
+    const response = { url: () => "https://public.example/a.json", headers: () => ({}) };
+    discovery.collect(response);
+    discovery.collect(response);
+    let finish!: (response: Response) => void;
+    const fetchMock = vi.fn(
+      () =>
+        new Promise<Response>((resolve) => {
+          finish = resolve;
+        }),
+    );
+    vi.stubGlobal("fetch", fetchMock);
+    const budget = { remainingBytes: 1000 };
+    let settled = false;
+    const pending = discovery
+      .run(budget, () => 10000)
+      .then((result) => {
+        settled = true;
+        return result;
+      });
+    await Promise.resolve();
+    expect(settled).toBe(false);
+    finish(
+      new Response(JSON.stringify({ v: "5", w: 100, h: 100, fr: 30, ip: 0, op: 30, layers: [] })),
+    );
+    expect(await pending).toHaveLength(1);
+    const remaining = budget.remainingBytes;
+    discovery.collect({ url: () => "https://public.example/late.json", headers: () => ({}) });
+    expect(await discovery.run(budget, () => 10000)).toEqual([]);
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+    expect(budget.remainingBytes).toBe(remaining);
+  });
+
+  it("caps ordinary JSON candidates and their aggregate byte consumption", async () => {
+    const discovery = new LottieDiscovery();
+    for (let n = 0; n < 100; n++)
+      discovery.collect({
+        url: () => `https://public.example/api/${n}`,
+        headers: () => ({ "content-type": "application/json" }),
+      });
+    const fetchMock = vi.fn(async (_url: string | URL | Request) => new Response("{}"));
+    vi.stubGlobal("fetch", fetchMock);
+    const budget = { remainingBytes: 1000 };
+    expect(await discovery.run(budget, () => 10000)).toEqual([]);
+    expect(fetchMock).toHaveBeenCalledTimes(32);
+    expect(budget.remainingBytes).toBe(936);
+  });
+  it("retains explicit JSON when a later archive displaces a generic candidate", async () => {
+    const discovery = new LottieDiscovery();
+    discovery.collect({ url: () => "https://public.example/real.json", headers: () => ({}) });
+    for (let n = 0; n < 31; n++)
+      discovery.collect({
+        url: () => `https://public.example/api/${n}`,
+        headers: () => ({ "content-type": "application/json" }),
+      });
+    discovery.collect({ url: () => "https://public.example/anim.lottie", headers: () => ({}) });
+    const fetchMock = vi.fn(async (_url: string | URL | Request) => new Response("{}"));
+    vi.stubGlobal("fetch", fetchMock);
+    await discovery.run({ remainingBytes: 1000 }, () => 10000);
+    const urls = fetchMock.mock.calls.map((call) => call[0]);
+    expect(urls).toContain("https://public.example/real.json");
+    expect(urls).not.toContain("https://public.example/api/0");
+    expect(urls).toHaveLength(31);
+  });
+  afterEach(() => vi.unstubAllGlobals());
+  it.each([undefined, "1"])(
+    "does not trust intercepted Content-Length %s or materialize Puppeteer bodies",
+    async (length) => {
+      const buffer = vi.fn(() => {
+        throw new Error("unbounded body read");
+      });
+      const response = {
+        url: () => "https://public.example/animation.json",
+        headers: () => ({
+          "content-type": "application/json",
+          ...(length ? { "content-length": length } : {}),
+        }),
+        buffer,
+      };
+      const cancel = vi.fn();
+      vi.stubGlobal(
+        "fetch",
+        vi.fn(
+          async () =>
+            new Response(
+              new ReadableStream({
+                pull(controller) {
+                  controller.enqueue(new Uint8Array(4));
+                },
+                cancel,
+              }),
+              { headers: length ? { "content-length": length } : {} },
+            ),
+        ),
+      );
+      expect(await discoverLottieResponse(response, { remainingBytes: 5 })).toBeNull();
+      expect(buffer).not.toHaveBeenCalled();
+      expect(cancel).toHaveBeenCalledOnce();
+    },
+  );
+  it("retains valid discovered JSON with its existing byte accounting", async () => {
+    const data = { v: "5.12.2", w: 100, h: 100, layers: [], fr: 30, ip: 0, op: 30 };
+    const body = JSON.stringify(data);
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async () => new Response(body)),
+    );
+    const budget = { remainingBytes: body.length };
+    const found = await discoverLottieResponse(
+      { url: () => "https://public.example/animation.json?version=1", headers: () => ({}) },
+      budget,
+    );
+    expect(found?.data).toEqual(data);
+    expect(found?.dataBudget).toBe(budget);
+    expect(budget.remainingBytes).toBe(0);
+  });
+});
diff --git a/packages/cli/src/capture/lottieDiscovery.ts b/packages/cli/src/capture/lottieDiscovery.ts
new file mode 100644
index 0000000000..c9361d269e
--- /dev/null
+++ b/packages/cli/src/capture/lottieDiscovery.ts
@@ -0,0 +1,105 @@
+import type { HTTPResponse } from "puppeteer-core";
+import type { DiscoveredLottie } from "./mediaCapture.js";
+import { safeFetch } from "./assetDownloader.js";
+import { readBoundedResponse, type DownloadByteBudget } from "./readBoundedResponse.js";
+import { validLottieJson } from "./lottieValidation.js";
+import { CAPTURE_USER_AGENT } from "./userAgent.js";
+
+/** Puppeteer exposes a fully buffered body; inspect candidates through a bounded stream instead. */
+export async function discoverLottieResponse(
+  response: Pick<HTTPResponse, "url" | "headers">,
+  budget: DownloadByteBudget,
+  timeoutMs = 10_000,
+): Promise<DiscoveredLottie | null> {
+  const url = response.url();
+  const pathname = new URL(url).pathname;
+  if (pathname.endsWith(".lottie")) return { url };
+  const contentType = response.headers()["content-type"] ?? "";
+  if (!pathname.endsWith(".json") && !/application\/json|text\/plain/i.test(contentType))
+    return null;
+  if (budget.remainingBytes <= 0) return null;
+  const fetched = await safeFetch(url, {
+    signal: AbortSignal.timeout(timeoutMs),
+    headers: { "User-Agent": CAPTURE_USER_AGENT },
+  });
+  if (!fetched?.ok) return null;
+  const bytes = await readBoundedResponse(fetched, 5_000_000, budget);
+  if (!bytes) return null;
+  const source = bytes.toString("utf8");
+  if (!validLottieJson(source)) return null;
+  const data: unknown = JSON.parse(source);
+  if (!hasDiscoveryFields(data)) return null;
+  return { url, data, dataBudget: budget };
+}
+
+function hasDiscoveryFields(data: unknown): data is Record<string, unknown> {
+  if (data === null || typeof data !== "object") return false;
+  return ["v", "ip", "op", "layers", "w", "h", "fr"].every((key) => key in data);
+}
+
+interface Candidate {
+  url: string;
+  contentType: string;
+  priority: number;
+}
+
+/** Own discovery work: response events only enqueue metadata, and run() joins every fetch. */
+export class LottieDiscovery {
+  private candidates = new Map<string, Candidate>();
+  private closed = false;
+
+  collect(response: Pick<HTTPResponse, "url" | "headers">): void {
+    if (this.closed) return;
+    const url = response.url();
+    if (this.candidates.has(url)) return;
+    const contentType = response.headers()["content-type"] ?? "";
+    const priority = candidatePriority(url, contentType);
+    if (priority === null) return;
+    if (this.candidates.size >= 32) {
+      const worst = [...this.candidates.values()]
+        .sort((a, b) => b.priority - a.priority)
+        .find((candidate) => candidate.priority > priority);
+      if (!worst) return;
+      this.candidates.delete(worst.url);
+    }
+    this.candidates.set(url, { url, contentType, priority });
+  }
+
+  async run(
+    sharedBudget: DownloadByteBudget,
+    remainingMs: () => number,
+  ): Promise<DiscoveredLottie[]> {
+    if (this.closed) return [];
+    this.closed = true;
+    const candidates = [...this.candidates.values()].sort((a, b) => a.priority - b.priority);
+    this.candidates.clear();
+    const deadline = Date.now() + Math.min(10_000, remainingMs());
+    const budget = { remainingBytes: Math.min(20 * 1024 * 1024, sharedBudget.remainingBytes) };
+    const found: DiscoveredLottie[] = [];
+    for (const candidate of candidates) {
+      const timeout = Math.floor(Math.min(deadline - Date.now(), remainingMs()));
+      if (timeout <= 0 || budget.remainingBytes <= 0 || found.length >= 10) break;
+      const before = budget.remainingBytes;
+      try {
+        const result = await discoverLottieResponse(
+          { url: () => candidate.url, headers: () => ({ "content-type": candidate.contentType }) },
+          budget,
+          timeout,
+        );
+        if (result) found.push({ ...result, dataBudget: sharedBudget });
+      } catch {
+        /* unavailable candidate */
+      } finally {
+        sharedBudget.remainingBytes -= before - budget.remainingBytes;
+      }
+    }
+    return found;
+  }
+}
+
+function candidatePriority(url: string, contentType: string): number | null {
+  const path = new URL(url).pathname;
+  if (path.endsWith(".lottie")) return 0;
+  if (path.endsWith(".json")) return 1;
+  return /application\/json|text\/plain/i.test(contentType) ? 2 : null;
+}
diff --git a/packages/cli/src/capture/lottiePreviewRequests.test.ts b/packages/cli/src/capture/lottiePreviewRequests.test.ts
new file mode 100644
index 0000000000..cf663e464f
--- /dev/null
+++ b/packages/cli/src/capture/lottiePreviewRequests.test.ts
@@ -0,0 +1,23 @@
+import { describe, expect, it } from "vitest";
+import { allowedLottieRequest, LOTTIE_RUNTIME_URL } from "./lottiePreviewRequests.js";
+
+describe("Lottie preview request policy", () => {
+  it("allows the pinned runtime and public image/font assets", () => {
+    expect(allowedLottieRequest(LOTTIE_RUNTIME_URL, "script")).toBe(true);
+    expect(allowedLottieRequest("https://cdn.example/image.png", "image")).toBe(true);
+    expect(allowedLottieRequest("https://cdn.example/font.woff2", "font")).toBe(true);
+    expect(allowedLottieRequest("data:image/png;base64,AA==", "image")).toBe(true);
+  });
+  it.each([
+    "http://127.0.0.1/a",
+    "http://169.254.169.254/a",
+    "http://[::1]/a",
+    "file:///etc/passwd",
+  ])("blocks private and local targets %s", (url) => {
+    expect(allowedLottieRequest(url, "image")).toBe(false);
+  });
+  it("blocks arbitrary scripts and navigations", () => {
+    expect(allowedLottieRequest("https://cdn.example/script.js", "script")).toBe(false);
+    expect(allowedLottieRequest("https://cdn.example/page", "document")).toBe(false);
+  });
+});
diff --git a/packages/cli/src/capture/lottiePreviewRequests.ts b/packages/cli/src/capture/lottiePreviewRequests.ts
new file mode 100644
index 0000000000..f2c0aea8df
--- /dev/null
+++ b/packages/cli/src/capture/lottiePreviewRequests.ts
@@ -0,0 +1,24 @@
+import type { Page } from "puppeteer-core";
+import { isPrivateUrl } from "./assetDownloader.js";
+
+export const LOTTIE_RUNTIME_URL =
+  "https://cdnjs.cloudflare.com/ajax/libs/lottie-web/5.12.2/lottie.min.js";
+
+/** Apply capture's URL policy to each preview request, including redirect targets. */
+export function allowedLottieRequest(url: string, resourceType: string): boolean {
+  if (url === LOTTIE_RUNTIME_URL) return true;
+  if (!["image", "font", "stylesheet"].includes(resourceType)) return false;
+  if (url.startsWith("data:") || url.startsWith("blob:")) return true;
+  return !isPrivateUrl(url);
+}
+
+export async function guardLottiePreviewRequests(page: Page): Promise<void> {
+  await page.setRequestInterception(true);
+  page.on("request", (request) => {
+    if (request.isInterceptResolutionHandled()) return;
+    const action = allowedLottieRequest(request.url(), request.resourceType())
+      ? request.continue()
+      : request.abort("blockedbyclient");
+    void action.catch(() => {});
+  });
+}
diff --git a/packages/cli/src/capture/lottieValidation.test.ts b/packages/cli/src/capture/lottieValidation.test.ts
new file mode 100644
index 0000000000..eec917baac
--- /dev/null
+++ b/packages/cli/src/capture/lottieValidation.test.ts
@@ -0,0 +1,66 @@
+import AdmZip from "adm-zip";
+import { describe, expect, it } from "vitest";
+import { MAX_LOTTIE_BYTES, readLottieArchive, validLottieJson } from "./lottieValidation.js";
+import { preflightLottieArchive } from "./lottieArchivePreflight.js";
+
+const animation = JSON.stringify({ w: 100, h: 100, fr: 30, ip: 0, op: 30, layers: [] });
+
+function archive(path: string, content = animation): Buffer {
+  const zip = new AdmZip();
+  zip.addFile(path, Buffer.from(content));
+  return zip.toBuffer();
+}
+
+describe("Lottie archive validation", () => {
+  it("rejects one deeply segmented name before constructing adm-zip entries", () => {
+    const bytes = archive(`a/${"x/".repeat(5000)}demo.json`);
+    expect(preflightLottieArchive(bytes)).toBe(false);
+    expect(readLottieArchive(bytes)).toBeNull();
+  });
+  it.each([0x06054b50, 0x06064b50, 0x07064b50])("rejects ambiguous footer marker %s", (marker) => {
+    const bytes = archive("a/demo.json");
+    const end = bytes.length - 22;
+    const injected = Buffer.alloc(4);
+    injected.writeUInt32LE(marker);
+    const ambiguous = Buffer.concat([bytes.subarray(0, end), injected, bytes.subarray(end)]);
+    expect(preflightLottieArchive(ambiguous)).toBe(false);
+  });
+  it("rejects excessive EOCD entry counts before entry materialization", () => {
+    const bytes = archive("a/demo.json");
+    const end = bytes.lastIndexOf(Buffer.from([0x50, 0x4b, 0x05, 0x06]));
+    bytes.writeUInt16LE(1000, end + 8);
+    bytes.writeUInt16LE(1000, end + 10);
+    expect(readLottieArchive(bytes)).toBeNull();
+  });
+  it.each(["a/demo.json", "animations/demo.json"])("preserves valid %s animation JSON", (path) => {
+    expect(readLottieArchive(archive(path))).toBe(animation);
+  });
+  it("rejects corrupt archives and traversal names", () => {
+    expect(readLottieArchive(Buffer.from("not a zip"))).toBeNull();
+    expect(readLottieArchive(archive("animations/../demo.json"))).toBeNull();
+  });
+  it.each([0, MAX_LOTTIE_BYTES + 1])("rejects an unsafe declared expansion size %s", (size) => {
+    const bytes = archive("a/demo.json");
+    const central = bytes.indexOf(Buffer.from([0x50, 0x4b, 0x01, 0x02]));
+    expect(central).toBeGreaterThan(0);
+    bytes.writeUInt32LE(size, central + 24);
+    expect(readLottieArchive(bytes)).toBeNull();
+  });
+});
+
+describe("Lottie JSON validation", () => {
+  it("accepts the supported animation shape", () => {
+    expect(validLottieJson(animation)).toBe(true);
+  });
+  it.each([
+    '{"w":100,"h":100,"layers":true}',
+    '{"w":100000,"h":100000,"layers":[]}',
+    '{"w":100,"h":100,"layers":[],"__proto__":{}}',
+    '{"w":100,"h":100,"layers":[],"fr":1e999}',
+    '{"w":100,"h":100,"layers":[true,null,"x"],"fr":30,"ip":0,"op":30}',
+    '{"w":100,"h":100,"layers":[],"fr":5e-324,"ip":0,"op":10000000}',
+    '{"w":100,"h":100,"layers":[],"assets":[{"layers":[false]}]}',
+  ])("rejects invalid animation data %s", (source) => {
+    expect(validLottieJson(source)).toBe(false);
+  });
+});
diff --git a/packages/cli/src/capture/lottieValidation.ts b/packages/cli/src/capture/lottieValidation.ts
new file mode 100644
index 0000000000..eb2e0c4f7c
--- /dev/null
+++ b/packages/cli/src/capture/lottieValidation.ts
@@ -0,0 +1,107 @@
+import AdmZip from "adm-zip";
+import { preflightLottieArchive, safeLottieArchivePath } from "./lottieArchivePreflight.js";
+
+export const MAX_LOTTIE_BYTES = 10 * 1024 * 1024;
+
+/** Read animation JSON without extracting remote archive paths onto the filesystem. */
+export function readLottieArchive(bytes: Buffer): string | null {
+  if (bytes.length > MAX_LOTTIE_BYTES) return null;
+  if (!preflightLottieArchive(bytes)) return null;
+  try {
+    const zip = new AdmZip(bytes);
+    if (zip.getEntryCount() > 256) return null;
+    const entries = zip.getEntries();
+    if (entries.length > 256) return null;
+    if (!validArchiveEntries(entries)) return null;
+    const animation = entries.find((entry) =>
+      /^(?:a|animations)\/[^/]+\.json$/.test(entry.entryName),
+    );
+    // adm-zip uses a positive expected size as zlib's maxOutputLength.
+    if (!animation || animation.header.size <= 0) return null;
+    const data = animation.getData();
+    if (data.length !== animation.header.size || data.length > MAX_LOTTIE_BYTES) return null;
+    return data.toString("utf8");
+  } catch {
+    return null;
+  }
+}
+
+function validArchiveEntries(entries: { entryName: string; header: { size: number } }[]): boolean {
+  let total = 0;
+  for (const entry of entries) {
+    if (!safeLottieArchivePath(entry.entryName)) return false;
+    const size = entry.header.size;
+    if (!Number.isSafeInteger(size) || size < 0 || size > MAX_LOTTIE_BYTES) return false;
+    total += size;
+    if (total > 50 * 1024 * 1024) return false;
+  }
+  return true;
+}
+
+function record(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function dimension(value: unknown): value is number {
+  return typeof value === "number" && Number.isFinite(value) && value > 0 && value <= 16384;
+}
+
+/** Keep original valid animation JSON while bounding the data consumed by lottie-web. */
+export function validLottieJson(source: string): boolean {
+  if (Buffer.byteLength(source) > MAX_LOTTIE_BYTES) return false;
+  try {
+    const value: unknown = JSON.parse(source);
+    if (!record(value) || !dimension(value.w) || !dimension(value.h)) return false;
+    if (value.w * value.h > 40_000_000 || !Array.isArray(value.layers)) return false;
+    return validLottieTiming(value) && boundedLottieTree(value);
+  } catch {
+    return false;
+  }
+}
+
+function validLottieTiming(value: Record<string, unknown>): boolean {
+  if (value.fr !== undefined && (typeof value.fr !== "number" || value.fr <= 0 || value.fr > 240))
+    return false;
+  if (![value.ip, value.op].every(validOptionalFrame)) return false;
+  const start = numberOr(value.ip, 0);
+  const end = numberOr(value.op, 0);
+  const rate = numberOr(value.fr, 30);
+  const duration = (end - start) / rate;
+  return Number.isFinite(duration) && duration >= 0 && duration <= 3600;
+}
+
+function numberOr(value: unknown, fallback: number): number {
+  return typeof value === "number" ? value : fallback;
+}
+
+function validOptionalFrame(frame: unknown): boolean {
+  return (
+    frame === undefined ||
+    (typeof frame === "number" && Number.isFinite(frame) && Math.abs(frame) <= 10_000_000)
+  );
+}
+
+function jsonChildren(value: unknown): [string, unknown][] {
+  return value !== null && typeof value === "object" ? Object.entries(value) : [];
+}
+
+function boundedLottieTree(root: unknown): boolean {
+  const pending = [{ value: root, depth: 0 }];
+  let count = 0;
+  while (pending.length) {
+    const item = pending.pop()!;
+    if (++count > 100000 || item.depth > 128) return false;
+    if (typeof item.value === "number" && !Number.isFinite(item.value)) return false;
+    for (const [key, value] of jsonChildren(item.value)) {
+      if (!validLottieEntry(key, value)) return false;
+      if (count + pending.length >= 100000) return false;
+      pending.push({ value, depth: item.depth + 1 });
+    }
+  }
+  return true;
+}
+
+function validLottieEntry(key: string, value: unknown): boolean {
+  if (["__proto__", "constructor", "prototype"].includes(key)) return false;
+  return key !== "layers" || (Array.isArray(value) && value.every(record));
+}
diff --git a/packages/cli/src/capture/mediaCapture.test.ts b/packages/cli/src/capture/mediaCapture.test.ts
index f87a379ee1..b866370759 100644
--- a/packages/cli/src/capture/mediaCapture.test.ts
+++ b/packages/cli/src/capture/mediaCapture.test.ts
@@ -1,4 +1,12 @@
-import { existsSync, mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import {
+  existsSync,
+  mkdirSync,
+  mkdtempSync,
+  readFileSync,
+  readdirSync,
+  rmSync,
+  writeFileSync,
+} from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import type { Browser, Page } from "puppeteer-core";
@@ -56,6 +64,8 @@ describe("Lottie capture budget", () => {
 
     let remainingMs = 10_000;
     const previewPage = {
+      setRequestInterception: vi.fn(async () => undefined),
+      on: vi.fn(),
       setViewport: vi.fn(async () => undefined),
       setContent: vi.fn(async () => undefined),
       evaluate: vi.fn(async () => undefined),
@@ -96,6 +106,8 @@ describe("Lottie capture budget", () => {
 
     const screenshot = vi.fn(async () => undefined);
     const previewPage = {
+      setRequestInterception: vi.fn(async () => undefined),
+      on: vi.fn(),
       setViewport: vi.fn(async () => undefined),
       setContent: vi.fn(async () => undefined),
       evaluate: vi.fn(async () => undefined),
@@ -185,3 +197,24 @@ describe("remainingVideoDownloadTimeoutMs", () => {
     expect(remainingVideoDownloadTimeoutMs(1_000, 300_000, 2_000)).toBe(120_000);
   });
 });
+
+describe("Lottie capture rejects unsafe persistence", () => {
+  it("does not write corrupt archives as raw Lottie files", async () => {
+    const dir = tempDir();
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async () => new Response("not a zip")),
+    );
+    expect(await saveLottieAnimations([{ url: "https://public.example/bad.lottie" }], dir)).toBe(0);
+    expect(readdirSync(dir)).toEqual([]);
+  });
+  it("does not publish truthy non-array layers", async () => {
+    const dir = tempDir();
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async () => new Response('{"w":100,"h":100,"layers":true}')),
+    );
+    expect(await saveLottieAnimations([{ url: "https://public.example/bad.json" }], dir)).toBe(0);
+    expect(readdirSync(dir)).toEqual([]);
+  });
+});
diff --git a/packages/cli/src/capture/mediaCapture.ts b/packages/cli/src/capture/mediaCapture.ts
index cd5832abe5..734802b373 100644
--- a/packages/cli/src/capture/mediaCapture.ts
+++ b/packages/cli/src/capture/mediaCapture.ts
@@ -12,16 +12,26 @@ import { mkdirSync, writeFileSync, readdirSync, readFileSync, statSync } from "n
 import { join, extname } from "node:path";
 import { isPrivateUrl, safeFetch } from "./assetDownloader.js";
 import { CAPTURE_USER_AGENT } from "./userAgent.js";
+import { MAX_LOTTIE_BYTES, readLottieArchive, validLottieJson } from "./lottieValidation.js";
+import { guardLottiePreviewRequests, LOTTIE_RUNTIME_URL } from "./lottiePreviewRequests.js";
+import {
+  readBoundedResponse,
+  createCaptureDownloadBudget,
+  type DownloadByteBudget,
+} from "./readBoundedResponse.js";
 
 /** Discovered Lottie item from network interception or DOM scan. */
 export interface DiscoveredLottie {
   url: string;
   data?: unknown;
+  /** Internal discovery accounting: avoid charging the same buffered data twice. */
+  dataBudget?: DownloadByteBudget;
   dimensions?: { w: number; h: number };
   frameRate?: number;
 }
 
 interface RemainingBudget {
+  byteBudget?: DownloadByteBudget;
   remainingMs?: () => number;
 }
 
@@ -41,6 +51,7 @@ export async function saveLottieAnimations(
   lottieDir: string,
   budget: RemainingBudget = {},
 ): Promise<number> {
+  const byteBudget = budget.byteBudget ?? createCaptureDownloadBudget();
   let savedCount = 0;
   const savedHashes = new Set<string>(); // Deduplicate by content
 
@@ -53,6 +64,12 @@ export async function saveLottieAnimations(
       if (lottieItem.data) {
         // Already have the JSON data from network interception
         jsonData = JSON.stringify(lottieItem.data);
+        const size = Buffer.byteLength(jsonData);
+        if (size > MAX_LOTTIE_BYTES) continue;
+        if (lottieItem.dataBudget !== byteBudget) {
+          if (size > byteBudget.remainingBytes) continue;
+          byteBudget.remainingBytes -= size;
+        }
       } else if (lottieItem.url) {
         const requestTimeoutMs = Math.min(10_000, liveRemainingMs(budget, 10_000));
         if (requestTimeoutMs <= 0) break;
@@ -62,36 +79,11 @@ export async function saveLottieAnimations(
           headers: { "User-Agent": CAPTURE_USER_AGENT },
         });
         if (!res || !res.ok) continue;
-        const buf = Buffer.from(await res.arrayBuffer());
-
-        if (lottieItem.url.endsWith(".lottie")) {
-          // dotLottie is a ZIP — extract the animation JSON
-          try {
-            const AdmZip = (await import("adm-zip")).default;
-            const zip = new AdmZip(buf);
-            const entries = zip.getEntries();
-            // Look for animation JSON in both v1 (animations/) and v2 (a/) paths
-            const animEntry = entries.find(
-              (e) =>
-                (e.entryName.startsWith("a/") || e.entryName.startsWith("animations/")) &&
-                e.entryName.endsWith(".json"),
-            );
-            if (animEntry) {
-              jsonData = animEntry.getData().toString("utf-8");
-            }
-          } catch {
-            // adm-zip not available or extraction failed — save raw .lottie
-            const hash = buf.toString("base64").slice(0, 100);
-            if (savedHashes.has(hash)) continue;
-            savedHashes.add(hash);
-            writeFileSync(join(lottieDir, `animation-${savedCount}.lottie`), buf);
-            savedCount++;
-            continue;
-          }
-        } else {
-          // Plain JSON file
-          jsonData = buf.toString("utf-8");
-        }
+        const buf = await readBoundedResponse(res, MAX_LOTTIE_BYTES, byteBudget);
+        if (!buf) continue;
+        jsonData = new URL(lottieItem.url).pathname.endsWith(".lottie")
+          ? (readLottieArchive(buf) ?? undefined)
+          : buf.toString("utf8");
       }
 
       if (jsonData) {
@@ -100,13 +92,7 @@ export async function saveLottieAnimations(
         if (savedHashes.has(hash)) continue;
         savedHashes.add(hash);
 
-        // Validate it's actually Lottie
-        try {
-          const parsed = JSON.parse(jsonData);
-          if (!parsed.layers || !parsed.w) continue;
-        } catch {
-          continue;
-        }
+        if (!validLottieJson(jsonData)) continue;
 
         writeFileSync(join(lottieDir, `animation-${savedCount}.json`), jsonData, "utf-8");
         savedCount++;
@@ -165,6 +151,7 @@ export async function renderLottiePreviews(
         if (liveRemainingMs(budget, 1) <= 0) break;
         previewPage = await chromeBrowser.newPage();
         if (liveRemainingMs(budget, 1) <= 0) break;
+        await guardLottiePreviewRequests(previewPage);
         await previewPage.setViewport({ width: 400, height: 400 });
         const animData = JSON.parse(readFileSync(join(lottieDir, file), "utf-8"));
         const midFrame = Math.floor(((raw.op || 0) - (raw.ip || 0)) * 0.3);
@@ -172,7 +159,7 @@ export async function renderLottiePreviews(
         await previewPage.setContent(
           `<!DOCTYPE html>
 <html><head>
-<script src="https://cdnjs.cloudflare.com/ajax/libs/lottie-web/5.12.2/lottie.min.js"></script>
+<script src="${LOTTIE_RUNTIME_URL}"></script>
 <style>*{margin:0;padding:0;background:transparent}#c{width:400px;height:400px}</style>
 </head><body><div id="c"></div></body></html>`,
           { waitUntil: "load", timeout: 10000 },