diff --git a/.changeset/safe-tools-open.md b/.changeset/safe-tools-open.md
new file mode 100644
index 000000000..e762502a1
--- /dev/null
+++ b/.changeset/safe-tools-open.md
@@ -0,0 +1,5 @@
+---
+"@callstack/repack-dev-server": patch
+---
+
+Validate `/open-url` requests before passing their targets to the operating system.
diff --git a/packages/dev-server/src/plugins/devtools/__tests__/devtoolsPlugin.test.ts b/packages/dev-server/src/plugins/devtools/__tests__/devtoolsPlugin.test.ts
new file mode 100644
index 000000000..c6f35db71
--- /dev/null
+++ b/packages/dev-server/src/plugins/devtools/__tests__/devtoolsPlugin.test.ts
@@ -0,0 +1,147 @@
+import Fastify, { type FastifyInstance } from 'fastify';
+import fastifyPlugin from 'fastify-plugin';
+import open from 'open';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import type { Server } from '../../../types.js';
+import devtoolsPlugin from '../devtoolsPlugin.js';
+
+vi.mock('open', () => ({
+  default: vi.fn(),
+}));
+
+const openMock = vi.mocked(open);
+
+async function createTestServer() {
+  const instance = Fastify();
+
+  await instance.register(
+    fastifyPlugin(
+      async (fastify) => {
+        fastify.decorate('wss', {
+          messageServer: {
+            broadcast: vi.fn(),
+          },
+        } as unknown as FastifyInstance['wss']);
+      },
+      { name: 'wss-plugin' }
+    )
+  );
+  await instance.register(devtoolsPlugin, {
+    delegate: {} as Server.Delegate,
+  });
+
+  return instance;
+}
+
+describe('devtoolsPlugin /open-url', () => {
+  let instance: FastifyInstance;
+
+  beforeEach(async () => {
+    openMock.mockResolvedValue({} as never);
+    instance = await createTestServer();
+  });
+
+  afterEach(async () => {
+    await instance.close();
+    vi.clearAllMocks();
+  });
+
+  it.each([
+    'https://reactnative.dev/docs/tutorial',
+    'http://localhost:8081/docs?platform=ios#debugging',
+    'https://[::1]:8081/path',
+    'https://example.com/a%20path?value=%24safe#fragment',
+  ])('should open the validated browser URL %s', async (url) => {
+    const response = await instance.inject({
+      method: 'POST',
+      url: '/open-url',
+      payload: { url },
+    });
+
+    expect(response.statusCode).toBe(200);
+    expect(response.body).toBe('OK');
+    expect(openMock).toHaveBeenCalledOnce();
+    expect(openMock).toHaveBeenCalledWith(new URL(url).href);
+  });
+
+  it('should accept a text/plain JSON request body', async () => {
+    const url = 'https://reactnative.dev/docs/debugging';
+    const response = await instance.inject({
+      method: 'POST',
+      url: '/open-url',
+      headers: {
+        'content-type': 'text/plain',
+      },
+      payload: JSON.stringify({ url }),
+    });
+
+    expect(response.statusCode).toBe(200);
+    expect(openMock).toHaveBeenCalledWith(url);
+  });
+
+  it.each([
+    ['bare executable', 'calc.exe'],
+    ['Windows executable path', 'C:\\Windows\\System32\\calc.exe'],
+    ['POSIX application path', '/Applications/Calculator.app'],
+    ['UNC path', '\\\\server\\share\\payload.exe'],
+    ['file URL', 'file:///etc/passwd'],
+    ['JavaScript URL', 'javascript:alert(1)'],
+    ['data URL', 'data:text/html,<script>alert(1)</script>'],
+    ['custom URL scheme', 'ms-msdt:/id'],
+    ['PowerShell subexpression', 'https://example.invalid/$(calc.exe)'],
+    ['PowerShell environment expansion', 'https://example.invalid/$env:PATH'],
+    ['PowerShell escape character', 'https://example.invalid/?value=`whoami'],
+  ])('should reject a %s', async (_name, url) => {
+    const response = await instance.inject({
+      method: 'POST',
+      url: '/open-url',
+      payload: { url },
+    });
+
+    expect(response.statusCode).toBe(400);
+    expect(response.body).toBe('Invalid URL');
+    expect(openMock).not.toHaveBeenCalled();
+  });
+
+  it.each([
+    ['missing URL', {}],
+    ['non-string URL', { url: 123 }],
+    ['array body', [{ url: 'https://example.com' }]],
+  ])('should reject a request with a %s', async (_name, payload) => {
+    const response = await instance.inject({
+      method: 'POST',
+      url: '/open-url',
+      payload,
+    });
+
+    expect(response.statusCode).toBe(400);
+    expect(response.body).toBe('Invalid URL');
+    expect(openMock).not.toHaveBeenCalled();
+  });
+
+  it('should reject a request with no body', async () => {
+    const response = await instance.inject({
+      method: 'POST',
+      url: '/open-url',
+    });
+
+    expect(response.statusCode).toBe(400);
+    expect(response.body).toBe('Invalid URL');
+    expect(openMock).not.toHaveBeenCalled();
+  });
+
+  it('should reject malformed text/plain JSON', async () => {
+    const response = await instance.inject({
+      method: 'POST',
+      url: '/open-url',
+      headers: {
+        'content-type': 'text/plain',
+      },
+      payload: 'not JSON',
+    });
+
+    expect(response.statusCode).toBe(400);
+    expect(response.body).toBe('Invalid URL');
+    expect(openMock).not.toHaveBeenCalled();
+  });
+});
diff --git a/packages/dev-server/src/plugins/devtools/devtoolsPlugin.ts b/packages/dev-server/src/plugins/devtools/devtoolsPlugin.ts
index 7ffe06063..f76442047 100644
--- a/packages/dev-server/src/plugins/devtools/devtoolsPlugin.ts
+++ b/packages/dev-server/src/plugins/devtools/devtoolsPlugin.ts
@@ -4,21 +4,51 @@ import launchEditor from 'launch-editor';
 import open from 'open';
 import type { Server } from '../../types.js';
 
-interface OpenURLRequestBody {
-  url: string;
-}
-
 interface OpenStackFrameRequestBody {
   file: string;
   lineNumber: number;
 }
 
+const INVALID_URL = 'Invalid URL';
+const POWERSHELL_INTERPOLATION_CHARACTERS = /[$`]/;
+
 function parseRequestBody<T>(body: unknown): T {
   if (typeof body === 'object') return body as T;
   if (typeof body === 'string') return JSON.parse(body) as T;
   throw new Error(`Unsupported body type: ${typeof body}`);
 }
 
+function validateURLForOpen(body: unknown): string {
+  const parsedBody = parseRequestBody<unknown>(body);
+  if (
+    typeof parsedBody !== 'object' ||
+    parsedBody === null ||
+    Array.isArray(parsedBody)
+  ) {
+    throw new Error(INVALID_URL);
+  }
+
+  const { url } = parsedBody as { url?: unknown };
+  if (typeof url !== 'string') {
+    throw new Error(INVALID_URL);
+  }
+
+  const parsedURL = new URL(url);
+  if (parsedURL.protocol !== 'http:' && parsedURL.protocol !== 'https:') {
+    throw new Error(INVALID_URL);
+  }
+
+  const normalizedURL = parsedURL.href;
+
+  // open@10 interpolates its target into a double-quoted PowerShell command on
+  // Windows. Reject characters that PowerShell expands inside those strings.
+  if (POWERSHELL_INTERPOLATION_CHARACTERS.test(normalizedURL)) {
+    throw new Error(INVALID_URL);
+  }
+
+  return normalizedURL;
+}
+
 async function devtoolsPlugin(
   instance: FastifyInstance,
   { delegate }: { delegate: Server.Delegate }
@@ -29,7 +59,14 @@ async function devtoolsPlugin(
     method: ['POST'],
     url: '/open-url',
     handler: async (request, reply) => {
-      const { url } = parseRequestBody<OpenURLRequestBody>(request.body);
+      let url: string;
+      try {
+        url = validateURLForOpen(request.body);
+      } catch {
+        reply.code(400).send(INVALID_URL);
+        return;
+      }
+
       await open(url);
       reply.send('OK');
     },