diff --git a/dom/file/tests/test_agentcluster_bloburl.js b/dom/file/tests/test_agentcluster_bloburl.js
new file mode 100644
index 000000000000..102786f181ca
--- /dev/null
+++ b/dom/file/tests/test_agentcluster_bloburl.js
@@ -0,0 +1,159 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+const { CookieXPCShellUtils } = ChromeUtils.import(
+  "resource://testing-common/CookieXPCShellUtils.jsm"
+);
+
+CookieXPCShellUtils.init(this);
+
+// Same agent cluster, all works fine: blobURLs can be opened.
+add_task(async () => {
+  do_get_profile();
+
+  const server = CookieXPCShellUtils.createServer({ hosts: ["example.org"] });
+
+  let result = new Promise(resolve => {
+    server.registerPathHandler("/result", (metadata, response) => {
+      resolve(metadata.queryString == "ok");
+
+      const body = "Done";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  server.registerPathHandler("/test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      let b = new Blob(["Hello world!"]);
+      let u = URL.createObjectURL(b);
+      fetch(u).then(r => r.text()).then(t => {
+         if (t !== "Hello world!") {
+           throw new Error(42);
+         }
+      }).then(() => fetch("/result?ok"), () => fetch("/result?failure")).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/test"
+  );
+
+  Assert.ok(await result, "BlobURL works");
+  await contentPage.close();
+});
+
+// Same agent cluster: frames
+add_task(async () => {
+  do_get_profile();
+
+  const server = CookieXPCShellUtils.createServer({ hosts: ["example.org"] });
+
+  let result = new Promise(resolve => {
+    server.registerPathHandler("/result", (metadata, response) => {
+      resolve(metadata.queryString == "ok");
+
+      const body = "Done";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  server.registerPathHandler("/iframe", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      fetch("${metadata.queryString}").then(r => r.text()).then(t => {
+         if (t !== "Hello world!") {
+           throw new Error(42);
+         }
+      }).then(() => fetch("/result?ok"), () => fetch("/result?failure")).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  server.registerPathHandler("/test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<iframe id="a"></iframe><script>
+      let b = new Blob(["Hello world!"]);
+      let u = URL.createObjectURL(b);
+      document.getElementById("a").src = "/iframe?" + u;
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/test"
+  );
+
+  Assert.ok(await result, "BlobURL works");
+  await contentPage.close();
+});
+
+// Cross agent cluster: different tabs
+add_task(async () => {
+  do_get_profile();
+
+  const server = CookieXPCShellUtils.createServer({ hosts: ["example.org"] });
+
+  let result = new Promise(resolve => {
+    server.registerPathHandler("/result", (metadata, response) => {
+      resolve(metadata.queryString == "ok");
+
+      const body = "Done";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  const step = new Promise(resolve => {
+    server.registerPathHandler("/step", (metadata, response) => {
+      resolve(metadata.queryString);
+      response.setStatusLine(metadata.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html", false);
+      const body = "Thanks!";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  server.registerPathHandler("/test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      let b = new Blob(["Hello world!"]);
+      let u = URL.createObjectURL(b);
+      fetch("/step?" + u).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/test"
+  );
+
+  const blobURL = await step;
+  Assert.ok(blobURL.length, "We have a blobURL");
+
+  server.registerPathHandler("/cross-test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      fetch("${metadata.queryString}").then(r => r.text()).then(t => {
+         if (t !== "Hello world!") {
+           throw new Error(42);
+         }
+      }).then(() => fetch("/result?ok"), () => fetch("/result?failure")).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage2 = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/cross-test?" + blobURL
+  );
+
+  Assert.ok(!(await result), "BlobURL should not work");
+  await contentPage.close();
+  await contentPage2.close();
+});
diff --git a/dom/file/tests/xpcshell.ini b/dom/file/tests/xpcshell.ini
index dc9faecf8c45..2f817948d328 100644
--- a/dom/file/tests/xpcshell.ini
+++ b/dom/file/tests/xpcshell.ini
@@ -4,3 +4,5 @@
 [test_createFile.js]
 [test_ipc_messagemanager_blob.js]
 skip-if = os == "android"
+[test_agentcluster_bloburl.js]
+skip-if = os == "android"