1 files changed, 28 insertions, 0 deletions
diff --git a/browser/components/originattributes/test/browser/test_firstParty_postMessage.html b/browser/components/originattributes/test/browser/test_firstParty_postMessage.html
new file mode 100644
index 0000000000..a056909e37
--- /dev/null
+++ b/browser/components/originattributes/test/browser/test_firstParty_postMessage.html
@@ -0,0 +1,28 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8"/>
+  <title>Test for Bug 1260931</title>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<script>
+function onload() {
+  let iframe1 = document.getElementById("iframe1");
+  iframe1.contentWindow.postMessage("HI", "https://example.net");
+}
+
+window.onmessage = function(evt) {
+  document.getElementById("message").textContent = evt.data;
+
+  let iframe2 = document.createElement("iframe");
+  iframe2.src = "dummy.html";
+  document.body.appendChild(iframe2);
+};
+</script>
+<body onload="onload()">
+  <div>
+    <iframe id="iframe1" src="test.html"></iframe>
+    <span id="message"></span>
+  </div>
+</body>
+</html>