Filter extension activity across all cookie banner detectors

Signed-off-by: Émile Ré <emile@probo.com>

packages/cookie-banner/src/detectors/cookie-detector.ts

@@ -14,17 +14,11 @@
 
 import { isDeletion, parseCookieName, parseMaxAgeSeconds } from "../cookie-utils";
 import type { Detector } from "./detector";
+import { isExtensionCaller, isExtensionContext } from "./extension-context";
 import { getInitiatorURL } from "./initiator";
 import type { ReportQueue } from "./report-queue";
 import type { DetectedCookieEntry } from "./types";
 
-const EXTENSION_URL_RE = /(?:chrome|moz|safari-web)-extension:\/\//;
-
-function isExtensionCaller(): boolean {
-  const stack = new Error().stack ?? "";
-  return EXTENSION_URL_RE.test(stack);
-}
-
 export class CookieDetector implements Detector {
   private readonly queue: ReportQueue;
   private readonly apiOrigin: string;
@@ -41,6 +35,8 @@ export class CookieDetector implements Detector {
   start(): void {
     this.queue.onNotFound(() => this.stop());
 
+    if (isExtensionContext()) return;
+
     const desc =
       Object.getOwnPropertyDescriptor(Document.prototype, "cookie") ??
       Object.getOwnPropertyDescriptor(HTMLDocument.prototype, "cookie");

packages/cookie-banner/src/detectors/extension-context.ts

@@ -0,0 +1,58 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+export const EXTENSION_URL_RE = /(?:chrome|moz|safari-web)-extension:\/\//;
+
+const EXTENSION_PROTOCOLS = new Set([
+  "chrome-extension:",
+  "moz-extension:",
+  "safari-web-extension:",
+]);
+
+// isExtensionCaller inspects the synchronous JS call stack for a frame
+// whose URL is a browser extension origin. It is a best-effort check:
+// some hooks (PerformanceObserver, browser internals firing events from
+// their own threads) will not carry the original injector frame, so a
+// `false` result does not guarantee the caller is first-party.
+export function isExtensionCaller(): boolean {
+  const stack = new Error().stack ?? "";
+  return EXTENSION_URL_RE.test(stack);
+}
+
+// extensionContext is evaluated once at module load. We capture
+// `document.currentScript?.src` here because that reference only
+// resolves while the loading script is still executing -- by the time
+// a detector's `start()` is called, currentScript will typically be
+// null. Computing this lazily would defeat the check.
+const extensionContext: boolean = (() => {
+  if (typeof location !== "undefined" && EXTENSION_PROTOCOLS.has(location.protocol)) {
+    return true;
+  }
+  if (typeof document !== "undefined") {
+    const src = document.currentScript instanceof HTMLScriptElement
+      ? document.currentScript.src
+      : null;
+    if (src && EXTENSION_URL_RE.test(src)) return true;
+  }
+  return false;
+})();
+
+// isExtensionContext reports whether the SDK itself is being executed
+// from inside a browser extension (either an extension page, or a
+// script loaded via an extension URL). Detectors use this to skip
+// pre-existing-state scans that have no caller stack to inspect and
+// would otherwise attribute the extension's own data to the host page.
+export function isExtensionContext(): boolean {
+  return extensionContext;
+}

packages/cookie-banner/src/detectors/resource-detector.ts

@@ -13,11 +13,10 @@
 // PERFORMANCE OF THIS SOFTWARE.
 
 import type { Detector } from "./detector";
+import { isExtensionCaller, isExtensionContext } from "./extension-context";
 import type { ReportQueue } from "./report-queue";
 import type { ResourceType } from "./types";
 
-const EXTENSION_URL_RE = /(?:chrome|moz|safari-web)-extension:\/\//;
-
 // Map browser-reported PerformanceResourceTiming.initiatorType to the
 // server-side tracker_resource_type. Anything we cannot classify is
 // dropped rather than reported as "other" to keep the table tidy.
@@ -71,10 +70,13 @@ export class ResourceDetector implements Detector {
   start(): void {
     this.queue.onNotFound(() => this.stop());
 
-    this.scanExisting();
     this.observeMutations();
     this.observePerformance();
     this.wrapServiceWorker();
+
+    if (isExtensionContext()) return;
+
+    this.scanExisting();
     this.scanServiceWorkers();
   }
 
@@ -205,7 +207,7 @@ export class ResourceDetector implements Detector {
   }
 
   private processResource(src: string, resourceType: ResourceType): void {
-    if (EXTENSION_URL_RE.test(src)) return;
+    if (isExtensionCaller()) return;
 
     let parsed: URL;
     try {

packages/cookie-banner/src/detectors/storage-detector.ts

@@ -13,17 +13,12 @@
 // PERFORMANCE OF THIS SOFTWARE.
 
 import type { Detector } from "./detector";
+import { isExtensionCaller, isExtensionContext } from "./extension-context";
 import { getInitiatorURL } from "./initiator";
 import type { ReportQueue } from "./report-queue";
 import type { DetectedStorageEntry, StorageSource } from "./types";
 
 const OWN_KEY_PREFIX = "probo_consent:";
-const EXTENSION_URL_RE = /(?:chrome|moz|safari-web)-extension:\/\//;
-
-function isExtensionCaller(): boolean {
-  const stack = new Error().stack ?? "";
-  return EXTENSION_URL_RE.test(stack);
-}
 
 export class StorageDetector implements Detector {
   private readonly queue: ReportQueue;
@@ -43,6 +38,9 @@ export class StorageDetector implements Detector {
     this.wrapStorage();
     this.wrapIndexedDB();
     this.wrapCacheStorage();
+
+    if (isExtensionContext()) return;
+
     this.scanExisting();
     this.scanCacheStorage();
   }
@@ -90,6 +88,7 @@ export class StorageDetector implements Detector {
 
     IDBFactory.prototype.open = function (name: string, version?: number) {
       const request = originalOpen.call(this, name, version);
+      if (isExtensionCaller()) return request;
       self.onIndexedDBOpen(name);
       return request;
     };
@@ -104,7 +103,9 @@ export class StorageDetector implements Detector {
     const self = this;
 
     caches.open = function (name: string): Promise<Cache> {
-      self.onCacheStorageOpen(name, "script");
+      if (!isExtensionCaller()) {
+        self.onCacheStorageOpen(name, "script");
+      }
       return originalOpen(name);
     };
   }