diff --git a/lib/sentry-filter.ts b/lib/sentry-filter.ts
index 90dc8a7..b50ec51 100644
--- a/lib/sentry-filter.ts
+++ b/lib/sentry-filter.ts
@@ -1,3 +1,5 @@
+import { shouldDropInjectedBrowserEvent } from "./sentry-injected-browser";
+
 // Surgical client-side Sentry noise filtering.
 //
 // This module holds the *decision* of whether a browser error event is one of
@@ -34,6 +36,7 @@ interface FilterableFrame {
   filename?: string;
   abs_path?: string;
   module?: string;
+  function?: string;
 }
 
 interface FilterableException {
@@ -94,6 +97,8 @@ function frameIsKaltura(frame: FilterableFrame): boolean {
  * otherwise. Pure and side-effect-free.
  */
 export function shouldDropClientEvent(event: FilterableEvent): boolean {
+  if (shouldDropInjectedBrowserEvent(event)) return true;
+
   const exceptions = event.exception?.values ?? [];
 
   // 1. Kaltura player bundle frames (TRANSCRIPTS-2K, 2A). If any exception in
diff --git a/lib/sentry-injected-browser.test.ts b/lib/sentry-injected-browser.test.ts
new file mode 100644
index 0000000..dc340d0
--- /dev/null
+++ b/lib/sentry-injected-browser.test.ts
@@ -0,0 +1,122 @@
+import { describe, expect, it } from "vitest";
+import { shouldDropClientEvent } from "./sentry-filter";
+
+const page = { filename: "app:///en/login", function: "global code" };
+const bridge = {
+  filename: "app://navigation_performance_logger_android",
+  function: "sendDataToNative",
+};
+const app = { filename: "app:///lib/hooks/use-timezone.tsx", function: "read" };
+const signatures = [
+  ["ReferenceError", "Can't find variable: __firefox__", page],
+  [
+    "TypeError",
+    "undefined is not an object (evaluating 'window.__firefox__.reader')",
+    page,
+  ],
+  [
+    "TypeError",
+    "undefined is not an object (evaluating 'window.__firefox__.refresh_youtube_quality_C85C5288CC2B4BDCBB20C5778007F667')",
+    page,
+  ],
+  [
+    "Error",
+    "MetaMask extension not found",
+    { filename: "app:///scripts/inpage.js" },
+  ],
+  [
+    "i",
+    "Failed to connect to MetaMask",
+    { filename: "app:///scripts/inpage.js" },
+  ],
+  ["Error", "Error invoking postMessage: Java object is gone", bridge],
+] as const;
+
+function exception(type: string, value: string, frame = app) {
+  return { type, value, stacktrace: { frames: [frame] } };
+}
+
+describe("confirmed injected browser signatures", () => {
+  it.each(signatures)(
+    "drops %s: %s only at its external source",
+    (type, value, frame) => {
+      const error = { type, value, stacktrace: { frames: [frame] } };
+      expect(shouldDropClientEvent({ exception: { values: [error] } })).toBe(
+        true,
+      );
+    },
+  );
+
+  it.each(signatures)("retains %s: %s from application code", (type, value) => {
+    expect(
+      shouldDropClientEvent({
+        exception: { values: [exception(type, value)] },
+      }),
+    ).toBe(false);
+  });
+
+  it("retains application callers in a native logger stack", () => {
+    const error = exception("Error", signatures[5][1], bridge);
+    error.stacktrace.frames.unshift(app);
+    expect(shouldDropClientEvent({ exception: { values: [error] } })).toBe(
+      false,
+    );
+  });
+
+  it("drops the captured multi-frame native logger signature", () => {
+    const frames = ["sendINPMessage", "sendDataToNative"].map((name) => ({
+      filename: bridge.filename,
+      function: name,
+    }));
+    const error = {
+      type: "Error",
+      value: signatures[5][1],
+      stacktrace: { frames },
+    };
+    expect(shouldDropClientEvent({ exception: { values: [error] } })).toBe(
+      true,
+    );
+  });
+
+  it("retains a chain containing an application failure", () => {
+    const external = exception("Error", signatures[5][1], bridge);
+    const firstParty = exception(
+      "TypeError",
+      "Cannot read properties of undefined (reading 'name')",
+    );
+    expect(
+      shouldDropClientEvent({ exception: { values: [external, firstParty] } }),
+    ).toBe(false);
+  });
+
+  it.each([
+    "Cannot read properties of undefined (reading 'M_ID')",
+    "Failed to fetch",
+    "The operation is insecure.",
+    "Object captured as promise rejection with keys: category, code, data, severity",
+    "This operation was aborted",
+    "controller[kState].transformAlgorithm is not a function",
+  ])("retains unconfirmed or actionable failure: %s", (value) => {
+    expect(
+      shouldDropClientEvent({
+        exception: { values: [exception("Error", value)] },
+      }),
+    ).toBe(false);
+  });
+
+  it("does not classify stackless errors or unrelated bridge errors as injection", () => {
+    const value = signatures[5][1];
+    expect(
+      shouldDropClientEvent({
+        exception: { values: [{ type: "Error", value }] },
+      }),
+    ).toBe(false);
+    expect(
+      shouldDropClientEvent({
+        exception: {
+          values: [exception("Error", "Unexpected response", bridge)],
+        },
+      }),
+    ).toBe(false);
+  });
+});
diff --git a/lib/sentry-injected-browser.ts b/lib/sentry-injected-browser.ts
new file mode 100644
index 0000000..4e2dd28
--- /dev/null
+++ b/lib/sentry-injected-browser.ts
@@ -0,0 +1,77 @@
+// Only signatures attributed to injected browser scripts in the Sentry audit.
+// Unknown executors (including M_ID), storage and media errors stay visible.
+interface Frame {
+  filename?: string;
+  abs_path?: string;
+  function?: string;
+}
+
+interface Exception {
+  type?: string;
+  value?: string;
+  stacktrace?: { frames?: Frame[] };
+}
+
+interface BrowserEvent {
+  exception?: { values?: Exception[] };
+}
+
+const FIREFOX_MESSAGES = new Set([
+  "Can't find variable: __firefox__",
+  "undefined is not an object (evaluating 'window.__firefox__.reader')",
+  "undefined is not an object (evaluating 'window.__firefox__.refresh_youtube_quality_C85C5288CC2B4BDCBB20C5778007F667')",
+]);
+
+function source(frame: Frame): string {
+  return frame.abs_path ?? frame.filename ?? "";
+}
+
+function isInjectedFirefox(error: Exception, frames: Frame[]): boolean {
+  if (!FIREFOX_MESSAGES.has(error.value ?? "")) return false;
+  return frames.every(
+    (frame) =>
+      frame.function === "global code" &&
+      /^app:\/\/\/(en|fr|es|ar|ru|zh)(\/|$)/.test(source(frame)),
+  );
+}
+
+function isInjectedMetaMask(error: Exception, frames: Frame[]): boolean {
+  const known = [
+    "MetaMask extension not found",
+    "Failed to connect to MetaMask",
+  ];
+  return (
+    known.includes(error.value ?? "") &&
+    frames.every((frame) => source(frame) === "app:///scripts/inpage.js")
+  );
+}
+
+function isInjectedPerformanceLogger(
+  error: Exception,
+  frames: Frame[],
+): boolean {
+  return (
+    error.value === "Error invoking postMessage: Java object is gone" &&
+    frames.every(
+      (frame) =>
+        source(frame) === "app://navigation_performance_logger_android",
+    ) &&
+    frames[frames.length - 1].function === "sendDataToNative"
+  );
+}
+
+function isKnownInjection(error: Exception): boolean {
+  const frames = error.stacktrace?.frames ?? [];
+  if (frames.length === 0) return false;
+  return (
+    isInjectedFirefox(error, frames) ||
+    isInjectedMetaMask(error, frames) ||
+    isInjectedPerformanceLogger(error, frames)
+  );
+}
+
+export function shouldDropInjectedBrowserEvent(event: BrowserEvent): boolean {
+  const values = event.exception?.values ?? [];
+  // Keep mixed exception chains: an injected cause does not excuse an app bug.
+  return values.length > 0 && values.every(isKnownInjection);
+}