diff --git a/toolkit/components/antitracking/test/browser/browser.ini b/toolkit/components/antitracking/test/browser/browser.ini
index db5ffb62ead2..435746239c63 100644
--- a/toolkit/components/antitracking/test/browser/browser.ini
+++ b/toolkit/components/antitracking/test/browser/browser.ini
@@ -16,6 +16,7 @@ support-files = server.sjs
 [browser_blockingStorage.js]
 [browser_blockingWorkers.js]
 [browser_blockingMessaging.js]
+[browser_existingCookiesForSubresources.js]
 [browser_imageCache.js]
 support-files = image.sjs
 [browser_subResources.js]
diff --git a/toolkit/components/antitracking/test/browser/browser_existingCookiesForSubresources.js b/toolkit/components/antitracking/test/browser/browser_existingCookiesForSubresources.js
new file mode 100644
index 000000000000..31cca6afa5d6
--- /dev/null
+++ b/toolkit/components/antitracking/test/browser/browser_existingCookiesForSubresources.js
@@ -0,0 +1,183 @@
+ChromeUtils.import("resource://gre/modules/Services.jsm");
+
+add_task(async function() {
+  info("Starting subResources test");
+
+  await SpecialPowers.flushPrefEnv();
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["privacy.trackingprotection.enabled", false],
+    ["privacy.trackingprotection.pbmode.enabled", false],
+    ["privacy.trackingprotection.annotate_channels", true],
+  ]});
+
+  await UrlClassifierTestUtils.addTestTrackers();
+
+  info("Creating a new tab");
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_3RD_PARTY_PAGE);
+  gBrowser.selectedTab = tab;
+
+  let browser = gBrowser.getBrowserForTab(tab);
+  await BrowserTestUtils.browserLoaded(browser);
+
+  info("Loading tracking scripts and tracking images before restricting 3rd party cookies");
+  await ContentTask.spawn(browser, null, async function() {
+    // Let's load the script twice here.
+    {
+      let src = content.document.createElement("script");
+      let p = new content.Promise(resolve => { src.onload = resolve; });
+      content.document.body.appendChild(src);
+      src.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=script";
+      await p;
+    }
+    {
+      let src = content.document.createElement("script");
+      let p = new content.Promise(resolve => { src.onload = resolve; });
+      content.document.body.appendChild(src);
+      src.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=script";
+      await p;
+    }
+
+    // Let's load an image twice here.
+    {
+      let img = content.document.createElement("img");
+      let p = new content.Promise(resolve => { img.onload = resolve; });
+      content.document.body.appendChild(img);
+      img.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=image";
+      await p;
+    }
+    {
+      let img = content.document.createElement("img");
+      let p = new content.Promise(resolve => { img.onload = resolve; });
+      content.document.body.appendChild(img);
+      img.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=image";
+      await p;
+    }
+  });
+
+  await fetch("https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?result&what=image")
+    .then(r => r.text())
+    .then(text => {
+      is(text, 1, "Cookies received for images");
+    });
+
+  await fetch("https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?result&what=script")
+    .then(r => r.text())
+    .then(text => {
+      is(text, 1, "Cookies received for scripts");
+    });
+
+  info("Removing the tab");
+  BrowserTestUtils.removeTab(tab);
+
+  Services.perms.removeAll();
+
+  // Now set up our prefs
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["privacy.restrict3rdpartystorage.enabled", true],
+  ]});
+
+  info("Creating a new tab");
+  tab = BrowserTestUtils.addTab(gBrowser, TEST_TOP_PAGE);
+  gBrowser.selectedTab = tab;
+
+  browser = gBrowser.getBrowserForTab(tab);
+  await BrowserTestUtils.browserLoaded(browser);
+
+  info("Creating a 3rd party content");
+  await ContentTask.spawn(browser,
+                          { page: TEST_3RD_PARTY_PAGE,
+                            callback: (async _ => {}).toString(),
+                          },
+                          async function(obj) {
+    await new content.Promise(resolve => {
+      let ifr = content.document.createElement("iframe");
+      ifr.onload = function() {
+        info("Sending code to the 3rd party content");
+        ifr.contentWindow.postMessage(obj.callback, "*");
+      };
+
+      content.addEventListener("message", function msg(event) {
+        if (event.data.type == "finish") {
+          content.removeEventListener("message", msg);
+          resolve();
+          return;
+        }
+
+        if (event.data.type == "ok") {
+          ok(event.data.what, event.data.msg);
+          return;
+        }
+
+        if (event.data.type == "info") {
+          info(event.data.msg);
+          return;
+        }
+
+        ok(false, "Unknown message");
+      });
+
+      content.document.body.appendChild(ifr);
+      ifr.src = obj.page;
+    });
+  });
+
+  info("Loading tracking scripts and tracking images again");
+  await ContentTask.spawn(browser, null, async function() {
+    // Let's load the script twice here.
+    {
+      let src = content.document.createElement("script");
+      let p = new content.Promise(resolve => { src.onload = resolve; });
+      content.document.body.appendChild(src);
+      src.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=script";
+      await p;
+    }
+    {
+      let src = content.document.createElement("script");
+      let p = new content.Promise(resolve => { src.onload = resolve; });
+      content.document.body.appendChild(src);
+      src.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=script";
+      await p;
+    }
+
+    // Let's load an image twice here.
+    {
+      let img = content.document.createElement("img");
+      let p = new content.Promise(resolve => { img.onload = resolve; });
+      content.document.body.appendChild(img);
+      img.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=image";
+      await p;
+    }
+    {
+      let img = content.document.createElement("img");
+      let p = new content.Promise(resolve => { img.onload = resolve; });
+      content.document.body.appendChild(img);
+      img.src = "https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?what=image";
+      await p;
+    }
+  });
+
+  await fetch("https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?result&what=image")
+    .then(r => r.text())
+    .then(text => {
+      is(text, 0, "No cookie received for images.");
+    });
+
+  await fetch("https://tracking.example.org/browser/toolkit/components/antitracking/test/browser/subResources.sjs?result&what=script")
+    .then(r => r.text())
+    .then(text => {
+      is(text, 0, "No cookie received received for scripts.");
+    });
+
+  info("Removing the tab");
+  BrowserTestUtils.removeTab(tab);
+
+  UrlClassifierTestUtils.cleanupTestTrackers();
+});
+
+add_task(async function() {
+  info("Cleaning up.");
+  await new Promise(resolve => {
+    Services.clearData.deleteData(Ci.nsIClearDataService.CLEAR_ALL, value => resolve());
+  });
+});
+