diff --git a/apps/silverback-gatsby/src/templates/webform.tsx b/apps/silverback-gatsby/src/templates/webform.tsx
index 40aeb093f..7c12c7d68 100644
--- a/apps/silverback-gatsby/src/templates/webform.tsx
+++ b/apps/silverback-gatsby/src/templates/webform.tsx
@@ -45,6 +45,22 @@ const Webform: React.FC<
           marginLeft: '-0.25em',
           marginRight: '-0.25em',
         }}
+        cssStylesToInject={
+          location.search.includes('test-inject-css=true')
+            ? `
+                /*
+                  comment with special chars
+                  #$@;\`'()* 
+                */
+                * {
+                  color: green;
+                }
+                .form-item-optional-text-field {
+                  margin-bottom: 200px;
+                }
+              `
+            : undefined
+        }
       />
     </StandardLayout>
   );
diff --git a/packages/composer/amazeelabs/silverback_iframe_theme/iframeCommand.js b/packages/composer/amazeelabs/silverback_iframe_theme/iframeCommand.js
index c8d1ab048..6b3933273 100644
--- a/packages/composer/amazeelabs/silverback_iframe_theme/iframeCommand.js
+++ b/packages/composer/amazeelabs/silverback_iframe_theme/iframeCommand.js
@@ -82,23 +82,11 @@
     },
   };
 
-  // Ask parent for the base URL to adjust links.
   waitForParentIframe(function (parentIFrame) {
-    parentIFrame.sendMessage({ action: 'getBaseUrl' }, '*');
+    parentIFrame.sendMessage({ action: 'init' }, '*');
   });
 
-  // Update links using the given base URL.
-  window.addEventListener('message', (event) => {
-    // The message looks like this:
-    // [iFrameSizer]message:"silverback-iframe-base-url:http://localhost:8000"
-    var prefix = '[iFrameSizer]message:"silverback-iframe-base-url:';
-    if (typeof event.data !== 'string' || event.data.indexOf(prefix) !== 0) {
-      return;
-    }
-    var baseUrl = event.data.substr(
-      prefix.length,
-      event.data.length - prefix.length - 1,
-    );
+  var updateBaseUrlInLinks = (baseUrl) => {
     $('a:visible').each(function () {
       var $this = $(this);
       var href = $this.attr('href');
@@ -132,5 +120,58 @@
     });
     // This class is used by integration tests.
     $('body').addClass('silverback-iframe-links-processed');
+  };
+
+  var injectCssStyles = (styles) => {
+    var id = 'silverback-iframe-injected-styles';
+    var el = document.getElementById(id);
+    if (!el) {
+      el = document.createElement('style');
+      el.id = id;
+      document.head.appendChild(el);
+    }
+    el.textContent = styles;
+  };
+
+  window.addEventListener('message', (event) => {
+    var parsed = parseMessage(event.data);
+    if (!parsed) {
+      return;
+    }
+    if (parsed.type === 'init') {
+      updateBaseUrlInLinks(parsed.baseUrl);
+      if (parsed.injectStyles) {
+        injectCssStyles(parsed.injectStyles);
+      }
+    }
   });
+
+  /**
+   *
+   * @param {string} message
+   * @returns {{type: 'init', baseUrl: string, injectStyles: string | undefined} | null}
+   */
+  function parseMessage(message) {
+    if (typeof message !== 'string') {
+      return null;
+    }
+    var prefix = '[iFrameSizer]message:';
+    if (!message.startsWith(prefix)) {
+      return null;
+    }
+    var parsed = null;
+    try {
+      parsed = JSON.parse(message.substring(prefix.length));
+    } catch (e) {
+      return null;
+    }
+    if (
+      typeof parsed !== 'object' ||
+      typeof parsed.silverbackIframe !== 'object' ||
+      parsed.silverbackIframe.type !== 'init'
+    ) {
+      return null;
+    }
+    return parsed.silverbackIframe;
+  }
 })(jQuery, Drupal, drupalSettings);
diff --git a/packages/npm/@amazeelabs/silverback-iframe/src/components/SilverbackIframe.tsx b/packages/npm/@amazeelabs/silverback-iframe/src/components/SilverbackIframe.tsx
index 888fc7641..8117a7c2f 100644
--- a/packages/npm/@amazeelabs/silverback-iframe/src/components/SilverbackIframe.tsx
+++ b/packages/npm/@amazeelabs/silverback-iframe/src/components/SilverbackIframe.tsx
@@ -11,6 +11,11 @@ type OwnProps = {
   buildMessages: (htmlMessages: Array<string>) => JSX.Element | null;
   redirect: (url: string, htmlMessages?: Array<string>) => void;
   scroll?: (to: string, iframeWrapper: HTMLElement) => void;
+  /**
+   * Not recommended for using in production.
+   * Because injecting CSS takes time and produces flashing.
+   */
+  cssStylesToInject?: string;
 };
 
 type Props = OwnProps & IframeResizer.IframeResizerProps;
@@ -19,6 +24,7 @@ export const SilverbackIframe = ({
   buildMessages,
   redirect,
   scroll,
+  cssStylesToInject,
   ...iframeResizerProps
 }: Props) => {
   const silverbackIframeReference = useRef<HTMLDivElement>(null);
@@ -50,9 +56,15 @@ export const SilverbackIframe = ({
             if (!isIframeCommand(message)) {
               return;
             }
-            if (message.action === 'getBaseUrl') {
+            if (message.action === 'init') {
               iframeRef.current?.sendMessage(
-                `silverback-iframe-base-url:${window.location.origin}`,
+                {
+                  silverbackIframe: {
+                    type: 'init',
+                    baseUrl: window.location.origin,
+                    injectStyles: cssStylesToInject,
+                  },
+                },
                 '*',
               );
               return;
diff --git a/packages/npm/@amazeelabs/silverback-iframe/src/types/__tests__/iframe-command.ts b/packages/npm/@amazeelabs/silverback-iframe/src/types/__tests__/iframe-command.ts
index 6f27267dd..c2cb97ef3 100644
--- a/packages/npm/@amazeelabs/silverback-iframe/src/types/__tests__/iframe-command.ts
+++ b/packages/npm/@amazeelabs/silverback-iframe/src/types/__tests__/iframe-command.ts
@@ -22,8 +22,8 @@ const sets = [
     result: false,
   },
   {
-    case: 'getBaseUrl',
-    data: { action: 'getBaseUrl' },
+    case: 'init',
+    data: { action: 'init' },
     result: true,
   },
   {
diff --git a/packages/npm/@amazeelabs/silverback-iframe/src/types/iframe-command.ts b/packages/npm/@amazeelabs/silverback-iframe/src/types/iframe-command.ts
index 7a17c8de9..adc652fb9 100644
--- a/packages/npm/@amazeelabs/silverback-iframe/src/types/iframe-command.ts
+++ b/packages/npm/@amazeelabs/silverback-iframe/src/types/iframe-command.ts
@@ -1,5 +1,5 @@
-export type IframeCommandGetBaseUrl = {
-  action: 'getBaseUrl';
+export type IframeCommandInit = {
+  action: 'init';
 };
 
 export type IframeCommandRedirect = {
@@ -20,14 +20,17 @@ export type IframeCommandScroll = {
 };
 
 export type IframeCommand =
-  | IframeCommandGetBaseUrl
+  | IframeCommandInit
   | IframeCommandRedirect
   | IframeCommandOther
   | IframeCommandScroll;
 
 export const isIframeCommand = (variable: any): variable is IframeCommand => {
   if (typeof variable === 'object' && typeof variable.action === 'string') {
-    if (['getBaseUrl', 'scroll'].includes(variable.action)) {
+    if (variable.action === 'init') {
+      return true;
+    }
+    if (variable.action === 'scroll' && typeof variable.scroll === 'string') {
       return true;
     }
     if (
diff --git a/packages/tests/silverback-gatsby/package.json b/packages/tests/silverback-gatsby/package.json
index dcfa52117..c41be1e54 100644
--- a/packages/tests/silverback-gatsby/package.json
+++ b/packages/tests/silverback-gatsby/package.json
@@ -23,6 +23,8 @@
     "test:integration": "playwright install chromium && pnpm test:readonly && pnpm test:mutating",
     "test:readonly": "playwright test --pass-with-no-tests",
     "test:mutating": "playwright test --pass-with-no-tests -c playwright.config.mutating.ts",
+    "headed:readonly": "pnpm test:readonly --headed",
+    "headed:mutating": "pnpm test:mutating --headed",
     "dev:readonly": "DEBUG=pw:api pnpm test:readonly --ui",
     "dev:mutating": "DEBUG=pw:api pnpm test:mutating --ui"
   }
diff --git a/packages/tests/silverback-gatsby/specs/webform.spec.ts b/packages/tests/silverback-gatsby/specs/webform.spec.ts
new file mode 100644
index 000000000..146d8103e
--- /dev/null
+++ b/packages/tests/silverback-gatsby/specs/webform.spec.ts
@@ -0,0 +1,29 @@
+import { gatsby } from '@amazeelabs/silverback-playwright';
+import { expect, test } from '@playwright/test';
+
+import { getIframe } from '../../silverback-drupal/common';
+
+test('injected CSS styles', async ({ page }) => {
+  // Check if it isn't green by default.
+  await page.goto(`${gatsby.baseUrl}/en/form/for-testing-confirmation-options`);
+  await expect((await getIframe(page)).locator('h1')).not.toHaveCSS(
+    'color',
+    'rgb(0, 128, 0)',
+  );
+
+  // Inject CSS.
+  await page.goto(
+    `${gatsby.baseUrl}/en/form/for-testing-confirmation-options?test-inject-css=true`,
+  );
+  // Check if it's green.
+  await expect((await getIframe(page)).locator('h1')).toHaveCSS(
+    'color',
+    'rgb(0, 128, 0)',
+  );
+  // Check if we have additional margin at the bottom of the field.
+  await expect(
+    (await getIframe(page)).locator('.form-item-optional-text-field'),
+  ).toHaveCSS('margin-bottom', '200px');
+  // Check if the iframe was resized. We should still see the Submit button.
+  await expect((await getIframe(page)).locator('text=Submit')).toBeVisible();
+});