diff --git a/frontend/app/common/types.ts b/frontend/app/common/types.ts
index 98f6ef34..e5c3d193 100644
--- a/frontend/app/common/types.ts
+++ b/frontend/app/common/types.ts
@@ -1,4 +1,4 @@
-export interface User {
+export type User = {
   name: string;
   id: string;
   picture: string;
@@ -7,15 +7,10 @@ export interface User {
   block: boolean;
   verified: boolean;
   email_subscription?: boolean;
-}
+};
 
 /** data which is used on user-info page */
-export interface UserInfo {
-  id: User['id'];
-  name: string | '';
-  isDefaultPicture: boolean;
-  picture: string;
-}
+export type UserInfo = Pick<User, 'id' | 'name' | 'picture'>;
 
 export interface BlockedUser {
   id: string;
diff --git a/frontend/app/common/user-info-settings.ts b/frontend/app/common/user-info-settings.ts
index 79400215..357a8810 100644
--- a/frontend/app/common/user-info-settings.ts
+++ b/frontend/app/common/user-info-settings.ts
@@ -4,8 +4,6 @@ import type { UserInfo } from './types';
 
 export const userInfo: UserInfo = parseQuery();
 
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
-export const isDefaultPicture = ((userInfo.isDefaultPicture as any) as string) !== '1';
 export const id = userInfo.id;
 export const name = userInfo.name;
 export const picture = userInfo.picture;
diff --git a/frontend/app/components/auth-panel/auth-panel.tsx b/frontend/app/components/auth-panel/auth-panel.tsx
index 19134f87..c36bbcb6 100644
--- a/frontend/app/components/auth-panel/auth-panel.tsx
+++ b/frontend/app/components/auth-panel/auth-panel.tsx
@@ -75,9 +75,11 @@ class AuthPanelComponent extends Component<Props, State> {
   toggleUserInfoVisibility = () => {
     const { user } = this.props;
 
-    if (window.parent && user) {
-      postMessage({ isUserInfoShown: true, user });
+    if (user === null) {
+      return;
     }
+
+    postMessage({ isUserInfoShown: true, user });
   };
 
   renderAuthorized = (user: User) => {
diff --git a/frontend/app/components/dropdown/dropdown.tsx b/frontend/app/components/dropdown/dropdown.tsx
index 8fbf36ee..70af3682 100644
--- a/frontend/app/components/dropdown/dropdown.tsx
+++ b/frontend/app/components/dropdown/dropdown.tsx
@@ -4,6 +4,7 @@ import b from 'bem-react-helper';
 import { Theme } from 'common/types';
 import { sleep } from 'utils/sleep';
 import { Button } from 'components/button';
+import { parseMessage } from 'utils/postMessage';
 
 type Props = RenderableProps<{
   title: string;
@@ -133,12 +134,14 @@ export class Dropdown extends Component<Props, State> {
     });
   }
 
-  receiveMessage(e: { data: string | object }) {
+  receiveMessage(event: MessageEvent<{ clickOutside?: boolean }>) {
     try {
-      const data = typeof e.data === 'string' ? JSON.parse(e.data) : e.data;
+      const data = parseMessage(event);
+
+      if (!data || !data.clickOutside || !this.state.isActive) {
+        return;
+      }
 
-      if (!data.clickOutside) return;
-      if (!this.state.isActive) return;
       this.setState(
         {
           contentTranslateX: 0,
diff --git a/frontend/app/components/root/root.tsx b/frontend/app/components/root/root.tsx
index 3c45fbfc..3c305e3e 100644
--- a/frontend/app/components/root/root.tsx
+++ b/frontend/app/components/root/root.tsx
@@ -4,7 +4,7 @@ import b from 'bem-react-helper';
 import { IntlShape, useIntl, FormattedMessage, defineMessages } from 'react-intl';
 import clsx from 'clsx';
 
-import type { Sorting } from 'common/types';
+import type { Sorting, Theme } from 'common/types';
 import type { StoreState } from 'store';
 import {
   COMMENT_NODE_CLASSNAME_PREFIX,
@@ -39,7 +39,7 @@ import { ConnectedComment as Comment } from 'components/comment/connected-commen
 import { uploadImage, getPreview } from 'common/api';
 import { isUserAnonymous } from 'utils/isUserAnonymous';
 import { bindActions } from 'utils/actionBinder';
-import { postMessage } from 'utils/postMessage';
+import { postMessage, parseMessage } from 'utils/postMessage';
 import { useActions } from 'hooks/useAction';
 import { setCollapse } from 'store/thread/actions';
 import { logout } from 'components/auth/auth.api';
@@ -177,13 +177,10 @@ export class Root extends Component<Props, State> {
     }
   };
 
-  onMessage(event: { data: string | object }) {
-    if (!event.data) {
-      return;
-    }
-
+  onMessage(event: MessageEvent<{ theme?: Theme }>) {
     try {
-      const data = typeof event.data === 'string' ? JSON.parse(event.data) : event.data;
+      const data = parseMessage(event);
+
       if (data.theme && THEMES.includes(data.theme)) {
         this.props.setTheme(data.theme);
       }
diff --git a/frontend/app/embed.ts b/frontend/app/embed.ts
index 504c6d1a..4cd970fc 100644
--- a/frontend/app/embed.ts
+++ b/frontend/app/embed.ts
@@ -1,5 +1,6 @@
 import type { UserInfo, Theme } from 'common/types';
 import { BASE_URL, NODE_ID, COMMENT_NODE_CLASSNAME_PREFIX } from 'common/constants.config';
+import { parseMessage, ParentMessage } from 'utils/postMessage';
 
 if (document.readyState === 'loading') {
   document.addEventListener('DOMContentLoaded', init);
@@ -199,9 +200,7 @@ function createInstance(config: typeof window.remark_config) {
         this.closeEl.innerHTML = '&#10006;';
         this.closeEl.onclick = () => this.close();
       }
-      const queryUserInfo = `${query}&page=user-info&&id=${user.id}&name=${user.name}&picture=${
-        user.picture || ''
-      }&isDefaultPicture=${user.isDefaultPicture || 0}`;
+      const queryUserInfo = `${query}&page=user-info&&id=${user.id}&name=${user.name}&picture=${user.picture || ''}`;
       const iframe = createFrame({ host: BASE_URL, query: queryUserInfo, height: '100%', margin: '0' });
       this.node.appendChild(iframe);
       this.iframe = iframe;
@@ -265,9 +264,10 @@ function createInstance(config: typeof window.remark_config) {
     },
   };
 
-  function receiveMessages(event: { data?: string }): void {
+  function receiveMessages(event: MessageEvent<ParentMessage>): void {
     try {
-      const data = typeof event.data === 'string' ? JSON.parse(event.data) : event.data;
+      const data = parseMessage(event);
+
       if (data.remarkIframeHeight) {
         iframe.style.height = `${data.remarkIframeHeight}px`;
       }
@@ -278,7 +278,7 @@ function createInstance(config: typeof window.remark_config) {
 
       if (Object.prototype.hasOwnProperty.call(data, 'isUserInfoShown')) {
         if (data.isUserInfoShown) {
-          userInfo.init(data.user || {});
+          userInfo.init(data.user);
         } else {
           userInfo.close();
         }
@@ -297,25 +297,25 @@ function createInstance(config: typeof window.remark_config) {
     if (hash.indexOf(`#${COMMENT_NODE_CLASSNAME_PREFIX}`) === 0) {
       if (e) e.preventDefault();
 
-      iframe.contentWindow!.postMessage(JSON.stringify({ hash }), '*');
+      iframe.contentWindow!.postMessage({ hash }, '*');
     }
   }
 
   function postTitleToIframe(title: string) {
     if (iframe.contentWindow) {
-      iframe.contentWindow.postMessage(JSON.stringify({ title }), '*');
+      iframe.contentWindow.postMessage({ title }, '*');
     }
   }
 
   function postClickOutsideToIframe(e: MouseEvent) {
     if (iframe.contentWindow && !iframe.contains(e.target as Node)) {
-      iframe.contentWindow.postMessage(JSON.stringify({ clickOutside: true }), '*');
+      iframe.contentWindow.postMessage({ clickOutside: true }, '*');
     }
   }
 
   function changeTheme(theme: Theme) {
     if (iframe.contentWindow) {
-      iframe.contentWindow.postMessage(JSON.stringify({ theme }), '*');
+      iframe.contentWindow.postMessage({ theme }, '*');
     }
   }
 
diff --git a/frontend/app/utils/postMessage.ts b/frontend/app/utils/postMessage.ts
index f0a849db..da58dde1 100644
--- a/frontend/app/utils/postMessage.ts
+++ b/frontend/app/utils/postMessage.ts
@@ -1,22 +1,42 @@
-import { User } from 'common/types';
+import type { Theme, UserInfo } from 'common/types';
 
-export type Message =
-  | { inited: true }
-  | {
-      isUserInfoShown: true;
-      user: User;
-    }
-  | { isUserInfoShown: false }
-  | { scrollTo: number }
-  | { remarkIframeHeight: number };
+export type ParentMessage = {
+  inited?: true;
+  scrollTo?: number;
+  remarkIframeHeight?: number;
+} & (
+  | { isUserInfoShown: true; user: UserInfo }
+  | { isUserInfoShown: false; user?: never }
+  | { isUserInfoShown?: never; user?: never }
+);
+
+export type ChildMessage = {
+  theme?: Theme;
+};
+
+type AllMessages = ParentMessage & ChildMessage;
 
 /**
  * Sends message to parent window
  *
  * @returns request success of fail
  */
-export function postMessage(data: Message): boolean {
+export function postMessage(data: AllMessages): boolean {
   if (!window.parent || window.parent === window) return false;
-  window.parent.postMessage(JSON.stringify(data), '*');
+  window.parent.postMessage(data, '*');
   return true;
 }
+
+/**
+ * Parses data from post message that was received in iframe
+ *
+ * @param evt post message event
+ * @returns
+ */
+export function parseMessage<T>({ data }: MessageEvent<T>): T {
+  if (typeof data !== 'object' || data === null || Array.isArray(data)) {
+    return {} as T;
+  }
+
+  return data as T;
+}
diff --git a/frontend/templates/iframe.ejs b/frontend/templates/iframe.ejs
index 13dc9a82..4ff54472 100644
--- a/frontend/templates/iframe.ejs
+++ b/frontend/templates/iframe.ejs
@@ -134,7 +134,7 @@
       setInterval(function () {
         if (document.body.offsetHeight !== lastHeight && document.body.offsetHeight > 22) {
           lastHeight = document.body.offsetHeight;
-          window.parent.postMessage(JSON.stringify({ remarkIframeHeight: lastHeight }), '*');
+          window.parent.postMessage({ remarkIframeHeight: lastHeight }, '*');
         }
       }, 200);
 
@@ -142,7 +142,9 @@
 
       function receiveMessages(event) {
         try {
-          const data = typeof event.data === 'string' ? JSON.parse(event.data) : event.data;
+          const data = event.data;
+          const isObj = typeof data === 'object' && data !== null && !Array.isArray(data);
+          if (!isObj) return;
           const isItHash = data.hash && data.hash.indexOf('#') === 0;
 
           if (isItHash) {
@@ -170,7 +172,7 @@
                 return c;
               }, {});
 
-      window.parent.postMessage(JSON.stringify({ inited: true }), '*');
+      window.parent.postMessage({ inited: true }, '*');
     </script>
     <script>
       (function (d) {