diff --git a/app-config.yaml b/app-config.yaml
index b8d355e4..2ff2cbed 100644
--- a/app-config.yaml
+++ b/app-config.yaml
@@ -3,6 +3,8 @@ httpApi:
   fileSizeLimit: 1000000
   port: 1337
   allowedOrigins: '*'
+  webOrigins:
+    - 'http://localhost:5173'
   cookieSecret: 'secret'
   cookieDomain: 'localhost'
   oauth2:
diff --git a/src/infrastructure/config/index.ts b/src/infrastructure/config/index.ts
index 0a36f5e5..32ea0cb9 100644
--- a/src/infrastructure/config/index.ts
+++ b/src/infrastructure/config/index.ts
@@ -98,6 +98,18 @@ export const LoggingConfig = z.object({
 
 export type LoggingConfig = z.infer<typeof LoggingConfig>;
 
+/**
+ * Exact origin of the web app, e.g. 'https://notex.so'
+ * Wildcards, paths and trailing slashes are not allowed, because tokens are posted to this origin
+ */
+const WebOrigin = z.string().refine((value) => {
+  try {
+    return new URL(value).origin === value;
+  } catch {
+    return false;
+  }
+}, { message: 'Must be an exact origin like https://notex.so' });
+
 /**
  * MCP endpoint configuration
  */
@@ -118,6 +130,7 @@ const HttpApiConfig = z.object({
   cookieDomain: z.string(),
   accessTokenSecret: z.string(),
   allowedOrigins: z.union([z.array(z.string()), z.literal('*')]),
+  webOrigins: z.array(WebOrigin), // origins of the web app allowed to receive tokens after OAuth login
   oauth2: OAuth2Config,
   mcp: McpConfig,
 });
@@ -148,6 +161,7 @@ const defaultConfig: AppConfig = {
     cookieDomain: 'localhost',
     accessTokenSecret: 'accessTokenSecret',
     allowedOrigins: [],
+    webOrigins: [],
     oauth2: {
       google: {
         clientId: '',
diff --git a/src/presentation/http/http-api.ts b/src/presentation/http/http-api.ts
index ac57e80f..ab430129 100644
--- a/src/presentation/http/http-api.ts
+++ b/src/presentation/http/http-api.ts
@@ -235,6 +235,7 @@ export default class HttpApi implements Api {
       userService: domainServices.userService,
       authService: domainServices.authService,
       cookieDomain: this.config.cookieDomain,
+      webOrigins: this.config.webOrigins,
     });
 
     await this.server?.register(AuthRouter, {
diff --git a/src/presentation/http/router/oauth.test.ts b/src/presentation/http/router/oauth.test.ts
new file mode 100644
index 00000000..236a61c5
--- /dev/null
+++ b/src/presentation/http/router/oauth.test.ts
@@ -0,0 +1,125 @@
+import { describe, test, expect, vi } from 'vitest';
+import { runInNewContext } from 'node:vm';
+import fastify from 'fastify';
+import type { FastifyInstance } from 'fastify';
+import type { OAuth2Namespace } from '@fastify/oauth2';
+import type UserService from '@domain/service/user.js';
+import type AuthService from '@domain/service/auth.js';
+import { OauthSchema } from '@presentation/http/schema/OauthSchema.js';
+import { notFound } from '@presentation/http/decorators/index.js';
+import OauthRouter from '@presentation/http/router/oauth.js';
+
+const accessToken = 'access-token';
+const refreshToken = 'refresh-token';
+
+/**
+ * Creates server with oauth router only. Google token exchange and user lookup are stubbed
+ * @param webOrigins - origins allowed to receive tokens
+ * @param user - user returned by provider lookup
+ */
+async function createServer(webOrigins: string[], user: { id: number } | null = { id: 1 }): Promise<FastifyInstance> {
+  const server = fastify();
+
+  server.decorate('googleOAuth2', {
+    /* eslint-disable-next-line @typescript-eslint/naming-convention */
+    getAccessTokenFromAuthorizationCodeFlow: vi.fn().mockResolvedValue({ token: { access_token: 'google-access-token' } }),
+  } as unknown as OAuth2Namespace);
+  server.decorateReply('notFound', notFound);
+  server.addSchema(OauthSchema);
+
+  await server.register(OauthRouter, {
+    prefix: '/oauth',
+    userService: {
+      getUserByProvider: vi.fn().mockResolvedValue(user),
+    } as unknown as UserService,
+    authService: {
+      signAccessToken: vi.fn().mockReturnValue(accessToken),
+      signRefreshToken: vi.fn().mockResolvedValue(refreshToken),
+    } as unknown as AuthService,
+    cookieDomain: 'localhost',
+    webOrigins,
+  });
+
+  return server;
+}
+
+/**
+ * Runs script of the callback page against fake opener window
+ * @param html - page returned by the callback endpoint
+ * @returns arguments of every postMessage call
+ */
+function runCallbackPage(html: string): unknown[][] {
+  const script = /<script>([\s\S]*?)<\/script>/.exec(html)?.[1] ?? '';
+  const postMessage = vi.fn();
+
+  runInNewContext(script, {
+    window: {
+      opener: { postMessage },
+      close: vi.fn(),
+    },
+  });
+
+  return postMessage.mock.calls;
+}
+
+describe('OAuth API', () => {
+  describe('GET /oauth/google/callback', () => {
+    test('Posts tokens only to the configured web origin', async () => {
+      const server = await createServer(['https://notex.so']);
+
+      const response = await server.inject({
+        method: 'GET',
+        url: '/oauth/google/callback',
+      });
+
+      expect(response.statusCode).toBe(200);
+      expect(runCallbackPage(response.body)).toEqual([
+        [
+          {
+            accessToken,
+            refreshToken,
+          },
+          'https://notex.so',
+        ],
+      ]);
+    });
+
+    test('Posts tokens to each configured web origin exactly, never to "*"', async () => {
+      const server = await createServer(['https://notex.so', 'http://localhost:5173']);
+
+      const response = await server.inject({
+        method: 'GET',
+        url: '/oauth/google/callback',
+      });
+
+      const targetOrigins = runCallbackPage(response.body).map(([, origin]) => origin);
+
+      expect(targetOrigins).toEqual(['https://notex.so', 'http://localhost:5173']);
+    });
+
+    test('Does not post tokens when no web origins are configured', async () => {
+      const server = await createServer([]);
+
+      const response = await server.inject({
+        method: 'GET',
+        url: '/oauth/google/callback',
+      });
+
+      expect(response.statusCode).toBe(200);
+      expect(runCallbackPage(response.body)).toEqual([]);
+    });
+
+    test('Returns 404 without tokens when user is not found', async () => {
+      const server = await createServer(['https://notex.so'], null);
+
+      const response = await server.inject({
+        method: 'GET',
+        url: '/oauth/google/callback',
+      });
+
+      expect(response.statusCode).toBe(404);
+      expect(response.body).not.toContain(accessToken);
+      expect(response.body).not.toContain(refreshToken);
+    });
+  });
+});
diff --git a/src/presentation/http/router/oauth.ts b/src/presentation/http/router/oauth.ts
index 2dc01160..205c4db8 100644
--- a/src/presentation/http/router/oauth.ts
+++ b/src/presentation/http/router/oauth.ts
@@ -21,6 +21,11 @@ interface OauthRouterOptions {
    * Cookie domain for refresh and access tokens
    */
   cookieDomain: string;
+
+  /**
+   * Exact origins of the web app allowed to receive tokens via postMessage
+   */
+  webOrigins: string[];
 }
 
 /**
@@ -30,6 +35,10 @@ interface OauthRouterOptions {
  * @param done - callback
  */
 const OauthRouter: FastifyPluginCallback<OauthRouterOptions> = (fastify, opts, done) => {
+  if (opts.webOrigins.length === 0) {
+    fastify.log.warn('httpApi.webOrigins is empty, so Google login will not pass tokens to the web app');
+  }
+
   /**
    * Callback for Google oauth2. Google redirects to this endpoint after user authentication.
    */
@@ -65,6 +74,16 @@ const OauthRouter: FastifyPluginCallback<OauthRouterOptions> = (fastify, opts, d
     const accessToken = opts.authService.signAccessToken({ id: user.id });
     const refreshToken = await opts.authService.signRefreshToken(user.id);
 
+    /**
+     * Never use '*' as target origin: any site could open the login popup and receive the tokens.
+     * Browser delivers the message only when the opener origin exactly matches one of the allowed origins
+     */
+    const message = JSON.stringify({
+      accessToken,
+      refreshToken,
+    });
+    const targetOrigins = JSON.stringify(opts.webOrigins);
+
     /**
      * Show page with script passing parent window postMessage with tokens
      */
@@ -72,7 +91,11 @@ const OauthRouter: FastifyPluginCallback<OauthRouterOptions> = (fastify, opts, d
       <html>
         <head>
           <script>
-            window.opener.postMessage({ accessToken: '${accessToken}', refreshToken: '${refreshToken}' }, '*');
+            if (window.opener) {
+              ${targetOrigins}.forEach(function (origin) {
+                window.opener.postMessage(${message}, origin);
+              });
+            }
             window.close();
           </script>
         </head>