feat: add dashboard client script

dashboard.js

@@ -0,0 +1,31 @@
+// Front-end dashboard logic (runs in the browser).
+
+// VULN 1: DOM-based XSS — untrusted data from the URL fragment is written to
+// innerHTML, so #<img src=x onerror=alert(1)> executes in the victim's session.
+function renderTab() {
+  const name = decodeURIComponent(location.hash.slice(1));
+  document.getElementById('tab').innerHTML = 'Tab: ' + name;
+}
+
+// VULN 2: Insecure postMessage handler — no e.origin check, and the payload is
+// used as an HTML sink, so any window/frame can inject markup/script.
+window.addEventListener('message', (e) => {
+  document.getElementById('widget').innerHTML = e.data.html;
+});
+
+// VULN 3: Client-side Prototype Pollution — a user-controlled key path from the
+// query string is deep-set into an object, polluting Object.prototype
+// (e.g. ?k=__proto__.isAdmin&v=true).
+function setDeep(obj, path, value) {
+  const keys = path.split('.');
+  let cur = obj;
+  for (let i = 0; i < keys.length - 1; i++) {
+    cur = cur[keys[i]] = cur[keys[i]] || {};
+  }
+  cur[keys[keys.length - 1]] = value;
+}
+
+const params = new URLSearchParams(location.search);
+setDeep({}, params.get('k'), params.get('v'));
+
+renderTab();