diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index d13e6dc7..a019bb0e 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -12,6 +12,7 @@
         "ant-design-vue": "^4.2.6",
         "axios": "^1.7.9",
         "moment": "^2.30.1",
+        "otpauth": "^9.5.1",
         "qrious": "^4.0.2",
         "qs": "^6.13.1",
         "vue": "^3.5.13",
@@ -423,6 +424,17 @@
         "@emnapi/runtime": "^1.7.1"
       }
     },
+    "node_modules/@noble/hashes": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@noble/hashes/-/hashes-2.2.0.tgz",
+      "integrity": "sha512-IYqDGiTXab6FniAgnSdZwgWbomxpy9FtYvLKs7wCUs2a8RkITG+DFGO1DM9cr+E3/RgADRpFjrKVaJ1z6sjtEg==",
+      "engines": {
+        "node": ">= 20.19.0"
+      },
+      "funding": {
+        "url": "https://paulmillr.com/funding/"
+      }
+    },
     "node_modules/@oxc-project/types": {
       "version": "0.128.0",
       "resolved": "https://registry.npmjs.org/@oxc-project/types/-/types-0.128.0.tgz",
@@ -2219,6 +2231,17 @@
         "node": ">= 0.8.0"
       }
     },
+    "node_modules/otpauth": {
+      "version": "9.5.1",
+      "resolved": "https://registry.npmjs.org/otpauth/-/otpauth-9.5.1.tgz",
+      "integrity": "sha512-fJmDAHc8wImfqqqOXIlBvT1dEKrZK0Cmb2VEgScpNTolCz0PHh6ExUZGv4sLtOsWNaHCQlD+rRqaPgnoxFoZjQ==",
+      "dependencies": {
+        "@noble/hashes": "2.2.0"
+      },
+      "funding": {
+        "url": "https://github.com/hectorm/otpauth?sponsor=1"
+      }
+    },
     "node_modules/p-limit": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/p-limit/-/p-limit-3.1.0.tgz",
diff --git a/frontend/package.json b/frontend/package.json
index 9d4f6ffa..147cdd22 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -11,10 +11,11 @@
     "lint": "eslint src --ext .js,.vue"
   },
   "dependencies": {
-    "ant-design-vue": "^4.2.6",
     "@ant-design/icons-vue": "^7.0.1",
+    "ant-design-vue": "^4.2.6",
     "axios": "^1.7.9",
     "moment": "^2.30.1",
+    "otpauth": "^9.5.1",
     "qrious": "^4.0.2",
     "qs": "^6.13.1",
     "vue": "^3.5.13",
diff --git a/frontend/src/pages/settings/SecurityTab.vue b/frontend/src/pages/settings/SecurityTab.vue
new file mode 100644
index 00000000..562f40df
--- /dev/null
+++ b/frontend/src/pages/settings/SecurityTab.vue
@@ -0,0 +1,166 @@
+<script setup>
+import { reactive, ref } from 'vue';
+import { message } from 'ant-design-vue';
+
+import { HttpUtil, RandomUtil } from '@/utils';
+import SettingListItem from '@/components/SettingListItem.vue';
+import TwoFactorModal from './TwoFactorModal.vue';
+
+const props = defineProps({
+  allSetting: { type: Object, required: true },
+});
+
+// 2FA modal state — both the "set" (enabling) and "confirm" (changing
+// password / disabling) flows route through the same component.
+const tfa = reactive({
+  open: false,
+  title: '',
+  description: '',
+  token: '',
+  type: 'set',
+  // resolveConfirm is called by the modal's @confirm with the success bool;
+  // it then routes the value back to whichever flow opened the modal.
+  resolveConfirm: (_success) => {},
+});
+
+function openTfa({ title, description = '', token = '', type, onConfirm }) {
+  tfa.title = title;
+  tfa.description = description;
+  tfa.token = token;
+  tfa.type = type;
+  tfa.resolveConfirm = onConfirm;
+  tfa.open = true;
+}
+
+function onTfaConfirm(success) {
+  tfa.resolveConfirm(success);
+}
+
+const user = reactive({
+  oldUsername: '',
+  oldPassword: '',
+  newUsername: '',
+  newPassword: '',
+});
+const updating = ref(false);
+
+async function sendUpdateUser() {
+  updating.value = true;
+  try {
+    const msg = await HttpUtil.post('/panel/setting/updateUser', user);
+    if (msg?.success) {
+      // Force re-login at the standard logout path; basePath is handled
+      // by the Go router so a relative redirect is correct here.
+      const basePath = window.__X_UI_BASE_PATH__ || '';
+      window.location.replace(`${basePath}logout`);
+    }
+  } finally {
+    updating.value = false;
+  }
+}
+
+function updateUser() {
+  if (props.allSetting.twoFactorEnable) {
+    openTfa({
+      title: 'Confirm with 2FA',
+      description: 'Enter the current 6-digit code to change credentials.',
+      token: props.allSetting.twoFactorToken,
+      type: 'confirm',
+      onConfirm: (ok) => { if (ok) sendUpdateUser(); },
+    });
+  } else {
+    sendUpdateUser();
+  }
+}
+
+function toggleTwoFactor() {
+  // Switch read-only — the actual flip happens after the modal succeeds.
+  if (!props.allSetting.twoFactorEnable) {
+    const newToken = RandomUtil.randomBase32String();
+    openTfa({
+      title: 'Enable two-factor authentication',
+      token: newToken,
+      type: 'set',
+      onConfirm: (ok) => {
+        if (ok) {
+          message.success('Two-factor authentication enabled.');
+          props.allSetting.twoFactorToken = newToken;
+        }
+        props.allSetting.twoFactorEnable = ok;
+      },
+    });
+  } else {
+    openTfa({
+      title: 'Disable two-factor authentication',
+      description: 'Enter the current 6-digit code to disable 2FA.',
+      token: props.allSetting.twoFactorToken,
+      type: 'confirm',
+      onConfirm: (ok) => {
+        if (!ok) return;
+        message.success('Two-factor authentication disabled.');
+        props.allSetting.twoFactorEnable = false;
+        props.allSetting.twoFactorToken = '';
+      },
+    });
+  }
+}
+</script>
+
+<template>
+  <a-collapse default-active-key="1">
+    <a-collapse-panel key="1" header="Admin">
+      <SettingListItem paddings="small">
+        <template #title>Current username</template>
+        <template #control>
+          <a-input v-model:value="user.oldUsername" autocomplete="username" />
+        </template>
+      </SettingListItem>
+
+      <SettingListItem paddings="small">
+        <template #title>Current password</template>
+        <template #control>
+          <a-input-password v-model:value="user.oldPassword" autocomplete="current-password" />
+        </template>
+      </SettingListItem>
+
+      <SettingListItem paddings="small">
+        <template #title>New username</template>
+        <template #control>
+          <a-input v-model:value="user.newUsername" />
+        </template>
+      </SettingListItem>
+
+      <SettingListItem paddings="small">
+        <template #title>New password</template>
+        <template #control>
+          <a-input-password v-model:value="user.newPassword" autocomplete="new-password" />
+        </template>
+      </SettingListItem>
+
+      <a-list-item>
+        <a-space direction="horizontal" :style="{ padding: '0 20px' }">
+          <a-button type="primary" :loading="updating" @click="updateUser">Confirm</a-button>
+        </a-space>
+      </a-list-item>
+    </a-collapse-panel>
+
+    <a-collapse-panel key="2" header="Two-factor authentication">
+      <SettingListItem paddings="small">
+        <template #title>Enable 2FA</template>
+        <template #description>Require a 6-digit TOTP code on every panel login.</template>
+        <template #control>
+          <a-switch :checked="allSetting.twoFactorEnable" @click="toggleTwoFactor" />
+        </template>
+      </SettingListItem>
+    </a-collapse-panel>
+  </a-collapse>
+
+  <TwoFactorModal
+    v-model:open="tfa.open"
+    :title="tfa.title"
+    :description="tfa.description"
+    :token="tfa.token"
+    :type="tfa.type"
+    @confirm="onTfaConfirm"
+  />
+</template>
diff --git a/frontend/src/pages/settings/SettingsPage.vue b/frontend/src/pages/settings/SettingsPage.vue
index 26d5da84..493b6c88 100644
--- a/frontend/src/pages/settings/SettingsPage.vue
+++ b/frontend/src/pages/settings/SettingsPage.vue
@@ -15,6 +15,7 @@ import { useMediaQuery } from '@/composables/useMediaQuery.js';
 import AppSidebar from '@/components/AppSidebar.vue';
 import { useAllSetting } from './useAllSetting.js';
 import GeneralTab from './GeneralTab.vue';
+import SecurityTab from './SecurityTab.vue';
 
 const antdThemeConfig = computed(() => ({
   algorithm: themeState.isDark ? antdTheme.darkAlgorithm : antdTheme.defaultAlgorithm,
@@ -214,7 +215,7 @@ const alertVisible = ref(true);
                         <SafetyOutlined />
                         <span>Security</span>
                       </template>
-                      <a-empty description="Security — coming in 5d-iii" />
+                      <SecurityTab :all-setting="allSetting" />
                     </a-tab-pane>
                     <a-tab-pane key="3" class="tab-pane">
                       <template #tab>
diff --git a/frontend/src/pages/settings/TwoFactorModal.vue b/frontend/src/pages/settings/TwoFactorModal.vue
new file mode 100644
index 00000000..51518dd2
--- /dev/null
+++ b/frontend/src/pages/settings/TwoFactorModal.vue
@@ -0,0 +1,155 @@
+<script setup>
+import { nextTick, ref, watch } from 'vue';
+import { message } from 'ant-design-vue';
+import * as OTPAuth from 'otpauth';
+import QRious from 'qrious';
+
+import { ClipboardManager } from '@/utils';
+
+// Two flavors of this modal:
+//   • type='set' shows a QR code + manual key + a 6-digit verifier
+//     (used when enabling 2FA the first time);
+//   • type='confirm' shows just the 6-digit verifier (used when
+//     toggling 2FA off and when changing the admin user/password).
+//
+// Either way the parent supplies a `confirm(success: boolean)`
+// callback — we run it with `true` only if the entered code matches
+// the live TOTP value, otherwise `false`.
+
+const props = defineProps({
+  open: { type: Boolean, default: false },
+  title: { type: String, default: '' },
+  description: { type: String, default: '' },
+  token: { type: String, default: '' },
+  type: { type: String, default: 'set', validator: (v) => ['set', 'confirm'].includes(v) },
+});
+
+const emit = defineEmits(['update:open', 'confirm']);
+
+const enteredCode = ref('');
+const qrCanvas = ref(null);
+
+let totp = null;
+
+function buildTotp() {
+  totp = new OTPAuth.TOTP({
+    issuer: '3x-ui',
+    label: 'Administrator',
+    algorithm: 'SHA1',
+    digits: 6,
+    period: 30,
+    secret: props.token,
+  });
+}
+
+async function paintQr() {
+  await nextTick();
+  if (!qrCanvas.value || !totp) return;
+  // QRious draws into a <canvas>; we don't need a wrapping div.
+  // eslint-disable-next-line no-new
+  new QRious({
+    element: qrCanvas.value,
+    size: 200,
+    value: totp.toString(),
+    background: 'white',
+    backgroundAlpha: 0,
+    foreground: 'black',
+    padding: 2,
+    level: 'L',
+  });
+}
+
+watch(() => props.open, (next) => {
+  if (!next) return;
+  enteredCode.value = '';
+  if (props.token) {
+    buildTotp();
+    if (props.type === 'set') paintQr();
+  }
+});
+
+function close(success) {
+  emit('confirm', success);
+  emit('update:open', false);
+  enteredCode.value = '';
+}
+
+function onOk() {
+  if (!totp) return;
+  if (totp.generate() === enteredCode.value) {
+    close(true);
+  } else {
+    message.error('Invalid code — check your authenticator and try again.');
+  }
+}
+
+function onCancel() {
+  close(false);
+}
+
+async function copyToken() {
+  const ok = await ClipboardManager.copyText(props.token);
+  if (ok) message.success('Copied');
+}
+</script>
+
+<template>
+  <a-modal
+    :open="open"
+    :title="title"
+    :closable="true"
+    @cancel="onCancel"
+  >
+    <template v-if="type === 'set'">
+      <p>Scan the QR code with your authenticator app, then enter the 6-digit code it shows.</p>
+      <a-divider />
+      <p>Step 1 — Scan the QR code (click to copy the secret).</p>
+      <div class="qr-wrap">
+        <div class="qr-bg">
+          <canvas ref="qrCanvas" class="qr-cv" @click="copyToken" />
+        </div>
+        <span class="qr-token">{{ token }}</span>
+      </div>
+      <a-divider />
+      <p>Step 2 — Enter the 6-digit code from your authenticator.</p>
+      <a-input v-model:value="enteredCode" :style="{ width: '100%' }" />
+    </template>
+
+    <template v-else>
+      <p>{{ description }}</p>
+      <a-input v-model:value="enteredCode" :style="{ width: '100%' }" />
+    </template>
+
+    <template #footer>
+      <a-button @click="onCancel">Cancel</a-button>
+      <a-button type="primary" :disabled="enteredCode.length < 6" @click="onOk">Confirm</a-button>
+    </template>
+  </a-modal>
+</template>
+
+<style scoped>
+.qr-wrap {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 12px;
+}
+.qr-bg {
+  width: 180px;
+  height: 180px;
+  background: #fff;
+  padding: 4px;
+  border-radius: 6px;
+}
+.qr-cv {
+  cursor: pointer;
+  width: 100% !important;
+  height: 100% !important;
+}
+.qr-token {
+  font-size: 12px;
+  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
+  word-break: break-all;
+  text-align: center;
+}
+</style>