diff --git a/app/sovran_systemsos_web/server.py b/app/sovran_systemsos_web/server.py
index 267e96f..2f5b355 100644
--- a/app/sovran_systemsos_web/server.py
+++ b/app/sovran_systemsos_web/server.py
@@ -59,6 +59,11 @@ REBOOT_COMMAND = ["reboot"]
 ONBOARDING_FLAG = "/var/lib/sovran/onboarding-complete"
 AUTOLAUNCH_DISABLE_FLAG = "/var/lib/sovran/hub-autolaunch-disabled"
 
+# ── Legacy security check constants ──────────────────────────────
+
+SECURITY_STATUS_FILE  = "/var/lib/sovran/security-status"
+SECURITY_WARNING_FILE = "/var/lib/sovran/security-warning"
+
 # ── Tech Support constants ────────────────────────────────────────
 
 SUPPORT_KEY_FILE = "/root/.ssh/sovran_support_authorized"
@@ -2916,6 +2921,37 @@ async def api_domains_check(req: DomainCheckRequest):
     return {"domains": list(check_results)}
 
 
+# ── Legacy security check ─────────────────────────────────────────
+
+@app.get("/api/security/status")
+async def api_security_status():
+    """Return the legacy security status and warning message, if present.
+
+    Reads /var/lib/sovran/security-status and /var/lib/sovran/security-warning.
+    Returns {"status": "legacy", "warning": "<message>"} for legacy machines,
+    or {"status": "ok", "warning": ""} when the files are absent.
+    """
+    try:
+        with open(SECURITY_STATUS_FILE, "r") as f:
+            status = f.read().strip()
+    except FileNotFoundError:
+        status = "ok"
+
+    warning = ""
+    if status == "legacy":
+        try:
+            with open(SECURITY_WARNING_FILE, "r") as f:
+                warning = f.read().strip()
+        except FileNotFoundError:
+            warning = (
+                "This machine was manufactured before the factory-seal process. "
+                "The default system password may be known to the factory. "
+                "Please change your system and application passwords immediately."
+            )
+
+    return {"status": status, "warning": warning}
+
+
 # ── Matrix user management ────────────────────────────────────────
 
 MATRIX_USERS_FILE = "/var/lib/secrets/matrix-users"
diff --git a/app/sovran_systemsos_web/static/css/security.css b/app/sovran_systemsos_web/static/css/security.css
new file mode 100644
index 0000000..513fc3d
--- /dev/null
+++ b/app/sovran_systemsos_web/static/css/security.css
@@ -0,0 +1,55 @@
+/* ── Legacy security warning modal ──────────────────────────────── */
+
+.security-warning-dialog {
+  max-width: 520px;
+}
+
+.security-warning-header {
+  background-color: #3b1212;
+  border-bottom-color: #7a2020;
+}
+
+.security-warning-body {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 16px;
+  padding: 24px 20px;
+}
+
+.security-warning-icon {
+  font-size: 2.5rem;
+}
+
+.security-warning-message {
+  text-align: center;
+  color: var(--text-primary);
+  line-height: 1.6;
+  margin: 0;
+}
+
+.security-warning-actions {
+  width: 100%;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 12px;
+}
+
+.security-warning-hint {
+  color: var(--text-secondary);
+  font-size: 0.85rem;
+  margin: 0;
+  text-align: center;
+}
+
+.security-warning-links {
+  display: flex;
+  gap: 12px;
+  flex-wrap: wrap;
+  justify-content: center;
+}
+
+.security-warning-link {
+  text-decoration: none;
+}
diff --git a/app/sovran_systemsos_web/static/js/events.js b/app/sovran_systemsos_web/static/js/events.js
index a39ef00..05e713b 100644
--- a/app/sovran_systemsos_web/static/js/events.js
+++ b/app/sovran_systemsos_web/static/js/events.js
@@ -38,6 +38,9 @@ if ($upgradeCloseBtn) $upgradeCloseBtn.addEventListener("click", closeUpgradeMod
 if ($upgradeCancelBtn) $upgradeCancelBtn.addEventListener("click", closeUpgradeModal);
 if ($upgradeModal) $upgradeModal.addEventListener("click", function(e) { if (e.target === $upgradeModal) closeUpgradeModal(); });
 
+// Legacy security warning modal — dismiss closes the modal only
+if ($securityWarningDismiss) $securityWarningDismiss.addEventListener("click", closeSecurityWarningModal);
+
 // ── Upgrade modal functions ───────────────────────────────────────
 
 function openUpgradeModal() {
@@ -84,6 +87,9 @@ async function init() {
     // If we can't reach the endpoint, continue to normal dashboard
   }
 
+  // Check for legacy machine security warning
+  await checkLegacySecurity();
+
   try {
     var cfg = await apiFetch("/api/config");
     _currentRole = cfg.role || "server_plus_desktop";
diff --git a/app/sovran_systemsos_web/static/js/security.js b/app/sovran_systemsos_web/static/js/security.js
new file mode 100644
index 0000000..096c3d4
--- /dev/null
+++ b/app/sovran_systemsos_web/static/js/security.js
@@ -0,0 +1,23 @@
+"use strict";
+
+// ── Legacy security warning ───────────────────────────────────────
+
+function openSecurityWarningModal(message) {
+  if ($securityWarningMessage) $securityWarningMessage.textContent = message;
+  if ($securityWarningModal) $securityWarningModal.classList.add("open");
+}
+
+function closeSecurityWarningModal() {
+  if ($securityWarningModal) $securityWarningModal.classList.remove("open");
+}
+
+async function checkLegacySecurity() {
+  try {
+    var data = await apiFetch("/api/security/status");
+    if (data && data.status === "legacy") {
+      openSecurityWarningModal(data.warning || "This machine may have a known factory password. Please change your passwords immediately.");
+    }
+  } catch (_) {
+    // Non-fatal — silently ignore if the endpoint is unreachable
+  }
+}
diff --git a/app/sovran_systemsos_web/static/js/state.js b/app/sovran_systemsos_web/static/js/state.js
index 896c372..597213a 100644
--- a/app/sovran_systemsos_web/static/js/state.js
+++ b/app/sovran_systemsos_web/static/js/state.js
@@ -99,5 +99,10 @@ const $upgradeConfirmBtn  = document.getElementById("upgrade-confirm-btn");
 const $upgradeCancelBtn   = document.getElementById("upgrade-cancel-btn");
 const $upgradeCloseBtn    = document.getElementById("upgrade-close-btn");
 
+// Legacy security warning modal
+const $securityWarningModal   = document.getElementById("security-warning-modal");
+const $securityWarningMessage = document.getElementById("security-warning-message");
+const $securityWarningDismiss = document.getElementById("security-warning-dismiss-btn");
+
 // System status banner
 // (removed — health is now shown per-tile via the composite health field)
\ No newline at end of file
diff --git a/app/sovran_systemsos_web/templates/index.html b/app/sovran_systemsos_web/templates/index.html
index 44746c3..2b014a6 100644
--- a/app/sovran_systemsos_web/templates/index.html
+++ b/app/sovran_systemsos_web/templates/index.html
@@ -14,6 +14,7 @@
   <link rel="stylesheet" href="/static/css/onboarding.css" />
   <link rel="stylesheet" href="/static/css/support.css" />
   <link rel="stylesheet" href="/static/css/domain-setup.css" />
+  <link rel="stylesheet" href="/static/css/security.css" />
 </head>
 <body>
 
@@ -209,6 +210,26 @@
     </div>
   </div>
 
+  <!-- Legacy Security Warning Modal -->
+  <div class="modal-overlay" id="security-warning-modal" role="alertdialog" aria-modal="true" aria-labelledby="security-warning-title">
+    <div class="creds-dialog security-warning-dialog">
+      <div class="creds-header security-warning-header">
+        <span class="creds-title" id="security-warning-title">⚠️ Security Warning</span>
+      </div>
+      <div class="creds-body security-warning-body">
+        <div class="security-warning-icon">🔒</div>
+        <p class="security-warning-message" id="security-warning-message"></p>
+        <div class="security-warning-actions">
+          <p class="security-warning-hint">Change your passwords now to secure your system:</p>
+          <div class="security-warning-links">
+            <a class="btn btn-primary security-warning-link" href="/onboarding?step=passwords" id="security-warning-change-btn">Change Passwords</a>
+            <button class="btn btn-close-modal" id="security-warning-dismiss-btn">I Understand — Dismiss</button>
+          </div>
+        </div>
+      </div>
+    </div>
+  </div>
+
   <!-- Reboot overlay -->
   <div class="reboot-overlay" id="reboot-overlay">
     <div class="reboot-card">
@@ -236,6 +257,7 @@
   <script src="/static/js/update.js"></script>
   <script src="/static/js/rebuild.js"></script>
   <script src="/static/js/features.js"></script>
+  <script src="/static/js/security.js"></script>
   <script src="/static/js/events.js"></script>
 </body>
 </html>
\ No newline at end of file