diff --git a/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step1.html b/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step1.html
index 7a66f3ab78..ecd6e26eca 100644
--- a/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step1.html
+++ b/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step1.html
@@ -1,29 +1,58 @@
-<!DOCTYPE html>
+<!doctype html>
 <html>
   <head>
     <meta charset="utf-8" />
   </head>
   <body>
-    <script>
-      if ("hasStorageAccess" in document) {
-        checkStorageAccess();
+    <script type="module">
+      // Check if the browser has granted us access to 3rd-party storage (such as cookies).
+      if (await hasStorageAccess()) {
+        // If so, signal support to the page embedding this iframe.
+        window.parent.postMessage("supported", "*");
       } else {
-        placeTestCookie();
+        // Otherwise, attempt to place a test cookie to verify support.
+        attemptWithTestCookie();
       }
 
-      function checkStorageAccess() {
-        document.hasStorageAccess().then(function (hasAccess) {
-          window.parent.postMessage(
-            hasAccess ? "supported" : "unsupported",
-            "*"
-          );
+      // See: https://developer.mozilla.org/en-US/docs/Web/API/Storage_Access_API/Using
+      async function hasStorageAccess() {
+        // If the Storage Access API is not implemented, assume we don't have access.
+        if (!("hasStorageAccess" in document)) {
+          return false;
+        }
+
+        const hasAccess = await document.hasStorageAccess();
+
+        // If we have access to unpartitioned cookies, signal support.
+        if (hasAccess) {
+          return true;
+        }
+
+        // Otherwise, check whether unpartitioned cookie access has been granted to another same-site embed.
+        const permission = await navigator.permissions.query({
+          name: "storage-access",
         });
+
+        // If not, signal that there is no support.
+        if (permission.state !== "granted") {
+          return false;
+        }
+
+        // Otherwise, call requestStorageAccess() without a user interaction, and it should resolve automatically.
+        // But just to be sure, handle a possible exception in case this behavior changes in the future.
+        try {
+          await document.requestStorageAccess();
+          return true;
+        } catch (error) {
+          return false;
+        }
       }
 
-      function placeTestCookie() {
-        document.cookie =
-          "KEYCLOAK_3P_COOKIE_SAMESITE=supported; Max-Age=60; SameSite=None; Secure";
+      function attemptWithTestCookie() {
+        // Place a cookie to test whether we can access cookies from 3rd-party storage.
+        document.cookie = "KEYCLOAK_3P_COOKIE_SAMESITE=supported; Max-Age=60; SameSite=None; Secure";
         document.cookie = "KEYCLOAK_3P_COOKIE=supported; Max-Age=60";
+        // Then redirect to the page where we will read these cookies to confirm this.
         window.location = "step2.html";
       }
     </script>
diff --git a/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step2.html b/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step2.html
index 36591b59b6..06a7f02335 100644
--- a/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step2.html
+++ b/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/3p-cookies-step2.html
@@ -1,17 +1,20 @@
-<!DOCTYPE html>
+<!doctype html>
 <html>
   <head>
     <meta charset="utf-8" />
   </head>
   <body>
-    <script>
-      var hasAccess = document.cookie.indexOf("KEYCLOAK_3P_COOKIE") !== -1;
+    <script type="module">
+      // Check if the previously placed cookies exist to detect support for 3rd-party access.
+      const hasAccess = document.cookie.includes("KEYCLOAK_3P_COOKIE");
 
+      // If so, clear the cookies, so they can no longer be used.
       if (hasAccess) {
         document.cookie = "KEYCLOAK_3P_COOKIE_SAMESITE=; Max-Age=0";
         document.cookie = "KEYCLOAK_3P_COOKIE=; Max-Age=0";
       }
 
+      // Signal 3rd-party access support to the page embedding this iframe.
       window.parent.postMessage(hasAccess ? "supported" : "unsupported", "*");
     </script>
   </body>
diff --git a/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/login-status-iframe.html b/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/login-status-iframe.html
index f1abfc2e41..01b31c1713 100755
--- a/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/login-status-iframe.html
+++ b/services/src/main/resources/org/keycloak/protocol/oidc/endpoints/login-status-iframe.html
@@ -1,125 +1,88 @@
-<!DOCTYPE html>
+<!doctype html>
 <html>
   <head>
     <meta charset="utf-8" />
   </head>
   <body>
-    <script>
-      var init;
+    <script type="module">
+      window.addEventListener("message", onMessage);
 
-      function checkState(clientId, origin, sessionState, callback) {
-        var cookie = getCookie();
-
-        var checkCookie = function () {
-          if (clientId === init.clientId && origin === init.origin) {
-            var c = cookie.split("/");
-            if (sessionState === c[2]) {
-              callback("unchanged");
-            } else {
-              callback("changed");
-            }
-          } else {
-            callback("error");
-          }
-        };
-
-        if (!init) {
-          var req = new XMLHttpRequest();
-
-          var url = location.href.split("?")[0] + "/init";
-          url += "?client_id=" + encodeURIComponent(clientId);
-          url += "&origin=" + encodeURIComponent(origin);
-
-          req.open("GET", url, true);
-
-          req.onreadystatechange = function () {
-            if (req.readyState === 4) {
-              if (req.status === 204 || req.status === 1223) {
-                init = {
-                  clientId: clientId,
-                  origin: origin,
-                };
-                if (!cookie) {
-                  if (sessionState != "") {
-                    callback("changed");
-                  } else {
-                    callback("unchanged");
-                  }
-                } else {
-                  checkCookie();
-                }
-              } else {
-                callback("error");
-              }
-            }
-          };
-
-          req.send();
-        } else if (!cookie) {
-          if (sessionState != "") {
-            callback("changed");
-          } else {
-            callback("unchanged");
-          }
-        } else {
-          checkCookie();
-        }
-      }
-
-      function getCookie() {
-        var cookie = getCookieByName("KEYCLOAK_SESSION");
-        if (cookie === null) {
-          return getCookieByName("KEYCLOAK_SESSION_LEGACY");
-        }
-        return cookie;
-      }
-
-      function getCookieByName(name) {
-        name = name + "=";
-        var ca = document.cookie.split(";");
-        for (var i = 0; i < ca.length; i++) {
-          var c = ca[i].trim();
-          if (c.indexOf(name) === 0) return c.substring(name.length, c.length);
-        }
-        return null;
-      }
-
-      function receiveMessage(event) {
+      async function onMessage(event) {
+        // Filter out any events that do not match the expected format of a 2-part string split by a space.
         if (typeof event.data !== "string") {
           return;
         }
 
-        var origin = event.origin;
-        var data = event.data.split(" ");
-        if (data.length != 2) {
+        const data = event.data.split(" ");
+
+        if (data.length !== 2) {
           return;
         }
 
-        var clientId = data[0];
-        var sessionState = data[1];
+        // Extract data from event and verify status of session.
+        const [clientId, sessionState] = data;
+        const sessionStatus = await checkState(clientId, event.origin, sessionState);
 
-        function doStateCheck() {
-          checkState(clientId, event.origin, sessionState, function (result) {
-            event.source.postMessage(result, origin);
-          });
-        }
-
-        if (!("hasStorageAccess" in document)) {
-          doStateCheck();
-          return;
-        }
-
-        document.hasStorageAccess().then(function (hasAccess) {
-          if (!hasAccess) {
-            event.source.postMessage("error");
-            return;
-          }
-
-          doStateCheck();
-        });
+        // Signal session status to the page embedding this iframe.
+        event.source.postMessage(sessionStatus, event.origin);
       }
 
-      window.addEventListener("message", receiveMessage, false);
+      let init;
+
+      async function checkState(clientId, origin, sessionState) {
+        const cookie = getSessionCookie();
+
+        // If not initialized, verify this client is allowed access with a call to the server.
+        if (!init) {
+          const url = new URL(`${location.origin}${location.pathname}/init`);
+
+          url.searchParams.set("client_id", clientId);
+          url.searchParams.set("origin", origin);
+
+          const response = await fetch(url);
+
+          if (!response.ok) {
+            return "error";
+          }
+
+          init = { clientId, origin };
+        }
+
+        // Signal a change in state if there is no cookie, and the session state is not empty.
+        if (!cookie) {
+          return sessionState !== "" ? "changed" : "unchanged";
+        }
+
+        // If the client and origin from the event match the verified ones from the server, signal if the cookie has changed.
+        if (clientId === init.clientId && origin === init.origin) {
+          const [, , cookieSessionState] = cookie.split("/");
+          return sessionState === cookieSessionState ? "unchanged" : "changed";
+        }
+
+        // Otherwise, if there is no match, then signal an error.
+        return "error";
+      }
+
+      function getSessionCookie() {
+        const cookie = getCookieByName("KEYCLOAK_SESSION");
+
+        if (cookie !== null) {
+          return cookie;
+        }
+
+        return getCookieByName("KEYCLOAK_SESSION_LEGACY");
+      }
+
+      function getCookieByName(name) {
+        const cookies = new Map();
+
+        for (const cookie of document.cookie.split(";")) {
+          const [key, value] = cookie.split("=").map((value) => value.trim());
+          cookies.set(key, value);
+        }
+
+        return cookies.get(name) ?? null;
+      }
     </script>
   </body>
 </html>
diff --git a/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/oauth/LoginStatusIframeEndpointTest.java b/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/oauth/LoginStatusIframeEndpointTest.java
index 0250c610a9..82cb2942b8 100644
--- a/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/oauth/LoginStatusIframeEndpointTest.java
+++ b/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/oauth/LoginStatusIframeEndpointTest.java
@@ -123,9 +123,6 @@ public class LoginStatusIframeEndpointTest extends AbstractKeycloakTest {
             response = client.execute(get);
 
             assertEquals(200, response.getStatusLine().getStatusCode());
-            s = IOUtils.toString(response.getEntity().getContent(), "UTF-8");
-            assertTrue(s.contains("function getCookie()"));
-
             assertEquals("CP=\"This is not a P3P policy!\"", response.getFirstHeader("P3P").getValue());
             assertNull(response.getFirstHeader(BrowserSecurityHeaders.X_FRAME_OPTIONS.getHeaderName()));
             assertEquals("frame-src 'self'; object-src 'none';", response.getFirstHeader(BrowserSecurityHeaders.CONTENT_SECURITY_POLICY.getHeaderName()).getValue());
