diff --git a/src/application/session/__tests__/sign_in.test.ts b/src/application/session/__tests__/sign_in.test.ts
new file mode 100644
index 00000000..853e3c20
--- /dev/null
+++ b/src/application/session/__tests__/sign_in.test.ts
@@ -0,0 +1,178 @@
+import { afterAuth, isSafeRedirectUrl, safeDecodeRedirectParam } from '../sign_in';
+
+// Mock localStorage
+const localStorageMock = (() => {
+  let store: Record<string, string> = {};
+  return {
+    getItem: (key: string) => store[key] ?? null,
+    setItem: (key: string, value: string) => {
+      store[key] = value;
+    },
+    removeItem: (key: string) => {
+      delete store[key];
+    },
+    clear: () => {
+      store = {};
+    },
+  };
+})();
+
+Object.defineProperty(window, 'localStorage', { value: localStorageMock });
+
+// Mock window.location (jsdom blocks direct href assignment)
+let hrefValue = 'http://localhost/login';
+Object.defineProperty(window, 'location', {
+  writable: true,
+  value: {
+    get href() {
+      return hrefValue;
+    },
+    set href(v: string) {
+      hrefValue = v;
+    },
+    origin: 'http://localhost',
+  },
+});
+
+beforeEach(() => {
+  localStorageMock.clear();
+  hrefValue = 'http://localhost/login';
+});
+
+describe('isSafeRedirectUrl', () => {
+  describe('safe URLs', () => {
+    it('returns true for a simple relative path', () => {
+      expect(isSafeRedirectUrl('/app')).toBe(true);
+    });
+
+    it('returns true for a relative path with query string', () => {
+      expect(isSafeRedirectUrl('/app?tab=settings')).toBe(true);
+    });
+
+    it('returns true for a relative path with nested segments', () => {
+      expect(isSafeRedirectUrl('/workspace/settings')).toBe(true);
+    });
+
+    it('returns true for an absolute URL matching window.location.origin', () => {
+      expect(isSafeRedirectUrl('http://localhost/app')).toBe(true);
+    });
+
+    it('returns true for an absolute URL with the same origin but a deep path', () => {
+      expect(isSafeRedirectUrl('http://localhost/workspace/abc/view/def')).toBe(true);
+    });
+  });
+
+  describe('unsafe URLs', () => {
+    it('returns false for an absolute URL with a different origin', () => {
+      expect(isSafeRedirectUrl('https://evil.com')).toBe(false);
+    });
+
+    it('returns false for an absolute URL with a different subdomain', () => {
+      expect(isSafeRedirectUrl('https://phishing.appflowy.com')).toBe(false);
+    });
+
+    it('returns false for a protocol-relative URL', () => {
+      expect(isSafeRedirectUrl('//evil.com')).toBe(false);
+    });
+
+    it('returns false for a javascript: URL', () => {
+      expect(isSafeRedirectUrl('javascript:alert(1)')).toBe(false);
+    });
+
+    it('returns false for a data: URL', () => {
+      expect(isSafeRedirectUrl('data:text/html,<script>alert(1)</script>')).toBe(false);
+    });
+
+    it('returns false for an empty string', () => {
+      expect(isSafeRedirectUrl('')).toBe(false);
+    });
+
+    it('returns false for a malformed string', () => {
+      expect(isSafeRedirectUrl('not a url at all %%')).toBe(false);
+    });
+
+    it('returns false for an http URL on a different host', () => {
+      expect(isSafeRedirectUrl('http://attacker.com/app')).toBe(false);
+    });
+  });
+});
+
+describe('afterAuth', () => {
+  it('redirects to /app when no redirectTo is stored', () => {
+    afterAuth();
+    expect(window.location.href).toBe('/app');
+  });
+
+  it('redirects to /app when stored redirectTo is an external URL', () => {
+    localStorage.setItem('redirectTo', encodeURIComponent('https://evil.com'));
+    afterAuth();
+    expect(window.location.href).toBe('/app');
+  });
+
+  it('redirects to /app when stored redirectTo is a protocol-relative URL', () => {
+    localStorage.setItem('redirectTo', encodeURIComponent('//evil.com/attack'));
+    afterAuth();
+    expect(window.location.href).toBe('/app');
+  });
+
+  it('redirects to /app when stored redirectTo contains a UUID path', () => {
+    const uuidPath = 'http://localhost/app/550e8400-e29b-41d4-a716-446655440000';
+    localStorage.setItem('redirectTo', encodeURIComponent(uuidPath));
+    afterAuth();
+    expect(window.location.href).toBe('/app');
+  });
+
+  it('redirects to /app path while preserving query params for root path', () => {
+    localStorage.setItem('redirectTo', encodeURIComponent('http://localhost/?foo=bar'));
+    afterAuth();
+    expect(window.location.href).toBe('http://localhost/app?foo=bar');
+  });
+
+  it('redirects to /app when stored redirectTo has malformed encoding', () => {
+    localStorage.setItem('redirectTo', '%zz');
+    afterAuth();
+    expect(window.location.href).toBe('/app');
+  });
+
+  it('follows a safe relative path', () => {
+    localStorage.setItem('redirectTo', encodeURIComponent('/settings'));
+    afterAuth();
+    expect(window.location.href).toBe('/settings');
+  });
+
+  it('follows a safe absolute same-origin URL', () => {
+    localStorage.setItem('redirectTo', encodeURIComponent('http://localhost/settings'));
+    afterAuth();
+    expect(window.location.href).toBe('http://localhost/settings');
+  });
+
+  it('clears localStorage after execution regardless of outcome', () => {
+    localStorage.setItem('redirectTo', encodeURIComponent('https://evil.com'));
+    afterAuth();
+    expect(localStorage.getItem('redirectTo')).toBeNull();
+  });
+
+  it('clears localStorage even for a safe redirect', () => {
+    localStorage.setItem('redirectTo', encodeURIComponent('/settings'));
+    afterAuth();
+    expect(localStorage.getItem('redirectTo')).toBeNull();
+  });
+});
+
+describe('safeDecodeRedirectParam', () => {
+  it('decodes a valid percent-encoded string', () => {
+    expect(safeDecodeRedirectParam('https%3A%2F%2Fevil.com')).toBe('https://evil.com');
+  });
+
+  it('returns the string unchanged when nothing is encoded', () => {
+    expect(safeDecodeRedirectParam('/settings')).toBe('/settings');
+  });
+
+  it('returns null for a malformed percent-encoded sequence', () => {
+    expect(safeDecodeRedirectParam('%zz')).toBeNull();
+  });
+
+  it('returns null for a lone percent sign', () => {
+    expect(safeDecodeRedirectParam('%')).toBeNull();
+  });
+});
diff --git a/src/application/session/sign_in.ts b/src/application/session/sign_in.ts
index 903816f2..f4bd54be 100644
--- a/src/application/session/sign_in.ts
+++ b/src/application/session/sign_in.ts
@@ -40,13 +40,55 @@ export function withSignIn() {
   };
 }
 
+/**
+ * Decodes a percent-encoded redirect parameter, returning null on malformed input
+ * so that bad values are always treated as unsafe rather than crashing.
+ */
+export function safeDecodeRedirectParam(value: string): string | null {
+  try {
+    return decodeURIComponent(value);
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Returns true only if the URL is safe to redirect to after authentication.
+ * Safe means: a relative path (starts with "/" but NOT "//") OR
+ * an absolute URL whose origin matches window.location.origin.
+ */
+export function isSafeRedirectUrl(url: string): boolean {
+  if (!url) return false;
+
+  // Relative path — safe (but "//evil.com" is protocol-relative, not safe)
+  if (url.startsWith('/') && !url.startsWith('//')) {
+    return true;
+  }
+
+  // Absolute URL — only safe if same origin
+  try {
+    const parsed = new URL(url);
+
+    return parsed.origin === window.location.origin;
+  } catch {
+    return false;
+  }
+}
+
 export function afterAuth() {
   const redirectTo = getRedirectTo();
 
   clearRedirectTo();
 
   if (redirectTo) {
-    const url = new URL(decodeURIComponent(redirectTo));
+    const decoded = safeDecodeRedirectParam(redirectTo);
+
+    if (!decoded || !isSafeRedirectUrl(decoded)) {
+      window.location.href = '/app';
+      return;
+    }
+
+    const url = new URL(decoded, window.location.origin);
     const pathname = url.pathname;
 
     // Check if URL contains workspace/view UUIDs (user-specific paths)
@@ -57,10 +99,11 @@ export function afterAuth() {
       // Don't redirect to user-specific pages from previous sessions
       window.location.href = '/app';
     } else if (pathname === '/' || !pathname) {
+      // Preserve query params and hash but redirect to /app path
       url.pathname = '/app';
       window.location.href = url.toString();
     } else {
-      window.location.href = url.toString();
+      window.location.href = decoded;
     }
   } else {
     window.location.href = '/app';
diff --git a/src/pages/LoginPage.tsx b/src/pages/LoginPage.tsx
index 14058ee1..7fbc9004 100644
--- a/src/pages/LoginPage.tsx
+++ b/src/pages/LoginPage.tsx
@@ -9,10 +9,11 @@ import { LOGIN_ACTION } from '@/components/login/const';
 import { EnterPassword } from '@/components/login/EnterPassword';
 import { ForgotPassword } from '@/components/login/ForgotPassword';
 import { SignUpPassword } from '@/components/login/SignUpPassword';
+import { isSafeRedirectUrl, safeDecodeRedirectParam } from '@/application/session/sign_in';
 import { AFConfigContext } from '@/components/main/app.hooks';
 
 function LoginPage() {
-  const [search] = useSearchParams();
+  const [search, setSearch] = useSearchParams();
   const action = search.get('action') || '';
   const email = search.get('email') || '';
   const force = search.get('force') === 'true';
@@ -21,15 +22,31 @@ function LoginPage() {
   const isAuthenticated = useContext(AFConfigContext)?.isAuthenticated || false;
 
 
+  // Strip unsafe redirectTo from URL immediately, preserving all other params
+  useEffect(() => {
+    if (!redirectTo) return;
+
+    const decodedRedirect = safeDecodeRedirectParam(redirectTo);
+
+    if (!decodedRedirect || !isSafeRedirectUrl(decodedRedirect)) {
+      setSearch((prev) => {
+        const next = new URLSearchParams(prev);
+
+        next.delete('redirectTo');
+        return next;
+      });
+    }
+  }, [redirectTo, setSearch]);
+
   useEffect(() => {
     if (action === LOGIN_ACTION.CHANGE_PASSWORD || force) {
       return;
     }
 
     if (isAuthenticated && redirectTo) {
-      const decodedRedirect = decodeURIComponent(redirectTo);
+      const decodedRedirect = safeDecodeRedirectParam(redirectTo);
 
-      if (decodedRedirect !== window.location.href) {
+      if (decodedRedirect && decodedRedirect !== window.location.href) {
         window.location.href = decodedRedirect;
       }
     }