diff --git a/web_src/js/markup/render-iframe.test.ts b/web_src/js/markup/render-iframe.test.ts
new file mode 100644
index 0000000000..53c9dc3720
--- /dev/null
+++ b/web_src/js/markup/render-iframe.test.ts
@@ -0,0 +1,46 @@
+import {navigateToIframeLink} from './render-iframe.ts';
+
+describe('navigateToIframeLink', () => {
+  const openSpy = vi.spyOn(window, 'open').mockImplementation(() => null);
+  const assignSpy = vi.spyOn(window.location, 'assign').mockImplementation(() => undefined);
+
+  test('safe links', () => {
+    navigateToIframeLink('http://example.com', '_blank');
+    expect(openSpy).toHaveBeenCalledWith('http://example.com/', '_blank', 'noopener,noreferrer');
+    vi.clearAllMocks();
+
+    navigateToIframeLink('https://example.com', '_self');
+    expect(assignSpy).toHaveBeenCalledWith('https://example.com/');
+    vi.clearAllMocks();
+
+    navigateToIframeLink('https://example.com', null);
+    expect(assignSpy).toHaveBeenCalledWith('https://example.com/');
+    vi.clearAllMocks();
+
+    navigateToIframeLink('/path', '');
+    expect(assignSpy).toHaveBeenCalledWith('http://localhost:3000/path');
+    vi.clearAllMocks();
+
+    // input can be any type & any value, keep the same behavior as `window.location.href = 0`
+    navigateToIframeLink(0, {});
+    expect(assignSpy).toHaveBeenCalledWith('http://localhost:3000/0');
+    vi.clearAllMocks();
+  });
+
+  test('unsafe links', () => {
+    window.location.href = 'http://localhost:3000/';
+
+    // eslint-disable-next-line no-script-url
+    navigateToIframeLink('javascript:void(0);', '_blank');
+    expect(openSpy).toHaveBeenCalledTimes(0);
+    expect(assignSpy).toHaveBeenCalledTimes(0);
+    expect(window.location.href).toBe('http://localhost:3000/');
+    vi.clearAllMocks();
+
+    navigateToIframeLink('data:image/svg+xml;utf8,<svg></svg>', '');
+    expect(openSpy).toHaveBeenCalledTimes(0);
+    expect(assignSpy).toHaveBeenCalledTimes(0);
+    expect(window.location.href).toBe('http://localhost:3000/');
+    vi.clearAllMocks();
+  });
+});
diff --git a/web_src/js/markup/render-iframe.ts b/web_src/js/markup/render-iframe.ts
index 1291dea4f8..531942e0b1 100644
--- a/web_src/js/markup/render-iframe.ts
+++ b/web_src/js/markup/render-iframe.ts
@@ -1,23 +1,46 @@
 import {generateElemId, queryElemChildren} from '../utils/dom.ts';
 import {isDarkTheme} from '../utils.ts';
 
+function safeRenderIframeLink(link: any): string | null {
+  try {
+    const url = new URL(`${link}`, window.location.href);
+    if (url.protocol !== 'http:' && url.protocol !== 'https:') {
+      console.error(`Unsupported link protocol: ${link}`);
+      return null;
+    }
+    return url.href;
+  } catch (e) {
+    console.error(`Failed to parse link: ${link}, error: ${e}`);
+    return null;
+  }
+}
+
+// This function is only designed for "open-link" command from iframe, is not suitable for other contexts.
+// Because other link protocols are directly handled by the iframe, but not here.
+// Arguments can be any type & any value, they are from "message" event's data which is not controlled by us.
+export function navigateToIframeLink(unsafeLink: any, target: any) {
+  const linkHref = safeRenderIframeLink(unsafeLink);
+  if (linkHref === null) return;
+  if (target === '_blank') {
+    window.open(linkHref, '_blank', 'noopener,noreferrer');
+    return;
+  }
+  // treat all other targets including ("_top", "_self", etc.) as same tab navigation
+  window.location.assign(linkHref);
+}
+
 async function loadRenderIframeContent(iframe: HTMLIFrameElement) {
   const iframeSrcUrl = iframe.getAttribute('data-src')!;
   if (!iframe.id) iframe.id = generateElemId('gitea-iframe-');
 
   window.addEventListener('message', (e) => {
+    if (e.source !== iframe.contentWindow) return;
     if (!e.data?.giteaIframeCmd || e.data?.giteaIframeId !== iframe.id) return;
     const cmd = e.data.giteaIframeCmd;
     if (cmd === 'resize') {
-      // TODO: sometimes the reported iframeHeight is not the size we need, need to figure why. Example: openapi swagger.
-      //  As a workaround, add some pixels here.
-      iframe.style.height = `${e.data.iframeHeight + 2}px`;
+      iframe.style.height = `${e.data.iframeHeight}px`;
     } else if (cmd === 'open-link') {
-      if (e.data.anchorTarget === '_blank') {
-        window.open(e.data.openLink, '_blank');
-      } else {
-        window.location.href = e.data.openLink;
-      }
+      navigateToIframeLink(e.data.openLink, e.data.anchorTarget);
     } else {
       throw new Error(`Unknown gitea iframe cmd: ${cmd}`);
     }
diff --git a/web_src/js/standalone/external-render-iframe.ts b/web_src/js/standalone/external-render-iframe.ts
index dcfeb50541..f8ec070785 100644
--- a/web_src/js/standalone/external-render-iframe.ts
+++ b/web_src/js/standalone/external-render-iframe.ts
@@ -20,7 +20,15 @@ function mainExternalRenderIframe() {
     window.parent.postMessage({giteaIframeCmd: cmd, giteaIframeId: iframeId, ...data}, '*');
   };
 
-  const updateIframeHeight = () => postIframeMsg('resize', {iframeHeight: document.documentElement.scrollHeight});
+  const updateIframeHeight = () => {
+    // Don't use integer heights from the DOM node.
+    // Use getBoundingClientRect(), then ceil the height to avoid fractional pixels which causes incorrect scrollbars.
+    const rect = document.documentElement.getBoundingClientRect();
+    postIframeMsg('resize', {iframeHeight: Math.ceil(rect.height)});
+    // As long as the parent page is responsible for the iframe height, the iframe itself doesn't need scrollbars.
+    // This style should only be dynamically set here when our code can run.
+    document.documentElement.style.overflowY = 'hidden';
+  };
   const resizeObserver = new ResizeObserver(() => updateIframeHeight());
   resizeObserver.observe(window.document.documentElement);
 
@@ -29,16 +37,18 @@ function mainExternalRenderIframe() {
   // the easiest way to handle dynamic content changes and easy to debug, can be fine-tuned in the future
   setInterval(updateIframeHeight, 1000);
 
-  //  no way to open an absolute link with CSP frame-src, it also needs some tricks like "postMessage" or "copy the link to clipboard"
-  const openIframeLink = (link: string, target: string) => postIframeMsg('open-link', {openLink: link, anchorTarget: target});
+  // no way to open an absolute link with CSP frame-src, it needs some tricks like "postMessage" (let parent window to handle) or "copy the link to clipboard" (let users manually paste it to open).
+  // here we choose "postMessage" way for better user experience.
+  const openIframeLink = (link: string, target: string | null) => postIframeMsg('open-link', {openLink: link, anchorTarget: target});
   document.addEventListener('click', (e) => {
     const el = e.target as HTMLAnchorElement;
     if (el.nodeName !== 'A') return;
-    const href = el.getAttribute('href') || '';
+    const href = el.getAttribute('href') ?? '';
     // safe links: "./any", "../any", "/any", "//host/any", "http://host/any", "https://host/any"
     if (href.startsWith('.') || href.startsWith('/') || href.startsWith('http://') || href.startsWith('https://')) {
       e.preventDefault();
-      openIframeLink(href, el.getAttribute('target')!);
+      const forceTarget = (e.metaKey || e.ctrlKey) ? '_blank' : null;
+      openIframeLink(href, forceTarget ?? el.getAttribute('target'));
     }
   });
 }