Security hardening, bug fixes, and per-tab alert icon

- Prevent fake finding injection via per-session nonce validation between
  MAIN world interceptor and ISOLATED world content script
- Fix CSV formula injection in export by sanitizing cell values
- Serialize storage writes to prevent race conditions across tabs
- Cap findings at 5000 with oldest-first eviction
- Delete findings by unique ID instead of URL to avoid collateral removal
- Validate keyword length (50 chars) and count (50 max)
- Add MutationObserver for SPA support (dynamic DOM scanning)
- Add explicit CSP to manifest
- Add per-tab alert icon with red dot overlay when secrets are found

js/background.js

@@ -1,5 +1,8 @@
 const KEYWORDS_KEY = "kf_keywords";
 const FINDINGS_KEY = "kf_findings";
+const MAX_FINDINGS = 5000;
+const MAX_KEYWORDS = 50;
+const MAX_KEYWORD_LENGTH = 50;
 
 const DEFAULT_KEYWORDS = [
   "key", "api_key", "apikey", "api-key", "secret", "token",
@@ -7,6 +10,76 @@ const DEFAULT_KEYWORDS = [
   "client_id", "client_secret"
 ];
 
+// Serialize all storage writes to prevent race conditions
+let storageQueue = Promise.resolve();
+function enqueue(fn) {
+  storageQueue = storageQueue.then(fn, fn);
+  return storageQueue;
+}
+
+// --- Per-tab alert icon ---
+const alertTabs = new Set();
+let alertIconCache = null;
+
+async function buildAlertIcons() {
+  if (alertIconCache) return alertIconCache;
+  const sizes = [16, 48];
+  const imageData = {};
+  for (const size of sizes) {
+    const resp = await fetch(chrome.runtime.getURL(`icons/icon${size}.png`));
+    const blob = await resp.blob();
+    const bitmap = await createImageBitmap(blob);
+    const canvas = new OffscreenCanvas(size, size);
+    const ctx = canvas.getContext("2d");
+    ctx.drawImage(bitmap, 0, 0, size, size);
+    // Red alert dot in top-right
+    const r = Math.max(3, Math.round(size * 0.22));
+    const cx = size - r - 1;
+    const cy = r + 1;
+    ctx.beginPath();
+    ctx.arc(cx, cy, r, 0, Math.PI * 2);
+    ctx.fillStyle = "#ff4444";
+    ctx.fill();
+    ctx.lineWidth = size >= 48 ? 2 : 1;
+    ctx.strokeStyle = "#0f0f0f";
+    ctx.stroke();
+    imageData[size] = ctx.getImageData(0, 0, size, size);
+  }
+  alertIconCache = imageData;
+  return imageData;
+}
+
+async function setAlertIcon(tabId) {
+  if (alertTabs.has(tabId)) return;
+  alertTabs.add(tabId);
+  try {
+    const imageData = await buildAlertIcons();
+    await chrome.action.setIcon({ tabId, imageData });
+  } catch {}
+}
+
+function resetTabIcon(tabId) {
+  if (!alertTabs.delete(tabId)) return;
+  try {
+    chrome.action.setIcon({
+      tabId,
+      path: { "16": "icons/icon16.png", "48": "icons/icon48.png", "128": "icons/icon128.png" }
+    });
+  } catch {}
+}
+
+// Reset icon when a tab navigates to a new page
+chrome.tabs.onUpdated.addListener((tabId, changeInfo) => {
+  if (changeInfo.status === "loading") {
+    resetTabIcon(tabId);
+  }
+});
+
+// Clean up when a tab is closed
+chrome.tabs.onRemoved.addListener((tabId) => {
+  alertTabs.delete(tabId);
+});
+
 chrome.runtime.onInstalled.addListener(async (details) => {
   if (details.reason === "install") {
     await chrome.storage.local.set({
@@ -18,7 +91,8 @@ chrome.runtime.onInstalled.addListener(async (details) => {
 
 chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
   if (request.type === "finding") {
-    saveFinding(request.data).then(() => sendResponse({ ok: true }));
+    if (sender.tab?.id) setAlertIcon(sender.tab.id);
+    enqueue(() => saveFinding(request.data)).then(() => sendResponse({ ok: true }));
     return true;
   }
   if (request.type === "getKeywords") {
@@ -30,19 +104,19 @@ chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
     return true;
   }
   if (request.type === "addKeyword") {
-    addKeyword(request.keyword).then((result) => sendResponse(result));
+    enqueue(() => addKeyword(request.keyword)).then((result) => sendResponse(result));
     return true;
   }
   if (request.type === "removeKeyword") {
-    removeKeyword(request.keyword).then(() => sendResponse({ ok: true }));
+    enqueue(() => removeKeyword(request.keyword)).then(() => sendResponse({ ok: true }));
     return true;
   }
   if (request.type === "removeFinding") {
-    removeFinding(request.url).then(() => sendResponse({ ok: true }));
+    enqueue(() => removeFinding(request.findingId)).then(() => sendResponse({ ok: true }));
     return true;
   }
   if (request.type === "clearFindings") {
-    clearFindings().then(() => sendResponse({ ok: true }));
+    enqueue(() => clearFindings()).then(() => sendResponse({ ok: true }));
     return true;
   }
   if (request.type === "exportFindings") {
@@ -60,6 +134,8 @@ async function addKeyword(keyword) {
   const keywords = await getKeywords();
   const normalized = keyword.trim().toLowerCase();
   if (!normalized) return { ok: false, error: "Keyword cannot be empty." };
+  if (normalized.length > MAX_KEYWORD_LENGTH) return { ok: false, error: `Keyword must be ${MAX_KEYWORD_LENGTH} characters or fewer.` };
+  if (keywords.length >= MAX_KEYWORDS) return { ok: false, error: `Maximum of ${MAX_KEYWORDS} keywords allowed.` };
   if (keywords.includes(normalized)) return { ok: false, error: "Keyword already exists." };
   keywords.push(normalized);
   await chrome.storage.local.set({ [KEYWORDS_KEY]: keywords });
@@ -82,7 +158,15 @@ async function saveFinding(finding) {
     (f) => f.url === finding.url && f.match === finding.match
   );
   if (isDuplicate) return;
+
+  finding.id = crypto.randomUUID();
   findings.push(finding);
+
+  // Evict oldest findings when cap is exceeded
+  if (findings.length > MAX_FINDINGS) {
+    findings.splice(0, findings.length - MAX_FINDINGS);
+  }
+
   await chrome.storage.local.set({ [FINDINGS_KEY]: findings });
 
   const badgeCount = findings.length;
@@ -90,9 +174,9 @@ async function saveFinding(finding) {
   chrome.action.setBadgeBackgroundColor({ color: "#e74c3c" });
 }
 
-async function removeFinding(url) {
+async function removeFinding(findingId) {
   const findings = await getFindings();
-  const updated = findings.filter((f) => f.url !== url);
+  const updated = findings.filter((f) => f.id !== findingId);
   await chrome.storage.local.set({ [FINDINGS_KEY]: updated });
   chrome.action.setBadgeText({ text: updated.length > 0 ? String(updated.length) : "" });
 }

js/content.js

@@ -294,9 +294,13 @@
     } catch {}
   }
 
+  const kfNonce = document.documentElement.getAttribute("data-kf-verify") || "";
+  document.documentElement.removeAttribute("data-kf-verify");
+
   window.addEventListener("__kf_finding__", (e) => {
     const data = e.detail;
     if (!data) return;
+    if (data.__kfNonce !== kfNonce) return;
 
     if (data.rawText) {
       scanText(data.rawText, data.sourceUrl || pageUrl, data.type);
@@ -327,6 +331,66 @@
   scanCookies();
   await scanExternalScripts();
 
+  // Observe DOM mutations for SPA support
+  const observer = new MutationObserver((mutations) => {
+    for (const mutation of mutations) {
+      for (const node of mutation.addedNodes) {
+        if (node.nodeType !== Node.ELEMENT_NODE) continue;
+        if (node.tagName === "SCRIPT") {
+          if (node.src) {
+            // New external script added
+            for (const kw of keywords) {
+              if (node.src.toLowerCase().includes(kw)) {
+                report({
+                  url: node.src, match: node.src, type: "script-src",
+                  patternName: `Script URL contains: ${kw}`,
+                  severity: "medium", confidence: "medium", provider: "URL Scan",
+                });
+              }
+            }
+          } else if (node.textContent) {
+            scanText(node.textContent, pageUrl, "inline-script");
+          }
+        }
+        // Scan any new hidden inputs
+        const hiddenInputs = node.matches && node.matches('input[type="hidden"]')
+          ? [node]
+          : (node.querySelectorAll ? Array.from(node.querySelectorAll('input[type="hidden"]')) : []);
+        for (const input of hiddenInputs) {
+          const name = (input.name || input.id || "").toLowerCase();
+          const value = input.value;
+          if (!value || value.length < 8) continue;
+          const sensitive = ["token", "csrf", "api_key", "apikey", "secret", "auth", "session", "nonce", "key", "access_token"];
+          if (sensitive.some((s) => name.includes(s)) || isHighEntropy(value)) {
+            report({
+              url: pageUrl, match: `${name}=${value.substring(0, 100)}`,
+              type: "hidden-input", patternName: "Hidden Form Field",
+              severity: isHighEntropy(value) ? "high" : "medium",
+              confidence: sensitive.some((s) => name.includes(s)) ? "high" : "medium",
+              provider: "DOM Scan",
+            });
+          }
+        }
+        // Scan data attributes on new elements
+        const elementsToCheck = node.querySelectorAll ? [node, ...node.querySelectorAll("*")] : [node];
+        for (const el of elementsToCheck) {
+          if (!el.attributes) continue;
+          for (const attr of el.attributes) {
+            if (!/^data-.*(?:key|token|secret|auth|api|credential|password)/i.test(attr.name)) continue;
+            if (!attr.value || attr.value.length < 8) continue;
+            report({
+              url: pageUrl, match: `${attr.name}="${attr.value.substring(0, 100)}"`,
+              type: "data-attribute", patternName: "Sensitive Data Attribute",
+              severity: "medium", confidence: isHighEntropy(attr.value) ? "high" : "medium",
+              provider: "DOM Scan",
+            });
+          }
+        }
+      }
+    }
+  });
+  observer.observe(document.body || document.documentElement, { childList: true, subtree: true });
+
   if (seen.size > 0) {
     console.log(`[KeyFinder] ${seen.size} potential secret(s) found on ${pageDomain}`);
   }

js/interceptor-loader.js

@@ -0,0 +1,16 @@
+(function () {
+  "use strict";
+
+  const nonce = crypto.randomUUID();
+
+  // Store nonce where both MAIN world (interceptor) and ISOLATED world (content.js) can read it.
+  // The interceptor removes data-kf-nonce after reading; data-kf-verify stays for content.js.
+  const el = document.documentElement;
+  el.setAttribute("data-kf-nonce", nonce);
+  el.setAttribute("data-kf-verify", nonce);
+
+  const script = document.createElement("script");
+  script.src = chrome.runtime.getURL("js/interceptor.js");
+  (document.head || document.documentElement).appendChild(script);
+  script.onload = () => script.remove();
+})();

js/interceptor.js

@@ -2,8 +2,11 @@
   "use strict";
 
   const EVENT_NAME = "__kf_finding__";
+  const nonce = document.documentElement.getAttribute("data-kf-nonce") || "";
+  document.documentElement.removeAttribute("data-kf-nonce");
 
   function emit(data) {
+    data.__kfNonce = nonce;
     window.dispatchEvent(new CustomEvent(EVENT_NAME, { detail: data }));
   }
 

js/results.js

@@ -173,8 +173,8 @@ function renderFindings() {
     delBtn.textContent = "Del";
     delBtn.title = "Remove finding";
     delBtn.addEventListener("click", async () => {
-      await chrome.runtime.sendMessage({ type: "removeFinding", url: f.url });
-      allFindings = allFindings.filter((x) => x !== f);
+      await chrome.runtime.sendMessage({ type: "removeFinding", findingId: f.id });
+      allFindings = allFindings.filter((x) => x.id !== f.id);
       renderStats();
       renderFindings();
     });
@@ -212,19 +212,26 @@ function exportJson() {
   downloadBlob(blob, `keyfinder-findings-${Date.now()}.json`);
 }
 
+function csvSafe(value) {
+  let str = String(value || "");
+  if (/^[=+\-@\t\r]/.test(str)) str = "'" + str;
+  str = str.replace(/"/g, '""');
+  return `"${str}"`;
+}
+
 function exportCsv() {
   const filtered = getFiltered();
   const headers = ["Severity", "Provider", "Pattern", "Match", "Type", "Domain", "URL", "Page URL", "Timestamp"];
   const rows = filtered.map((f) => [
-    f.severity || "",
-    f.provider || "",
-    f.patternName || "",
-    `"${(f.match || "").replace(/"/g, '""')}"`,
-    f.type || "",
-    f.domain || "",
-    f.url || "",
-    f.pageUrl || "",
-    f.timestamp ? new Date(f.timestamp).toISOString() : "",
+    csvSafe(f.severity),
+    csvSafe(f.provider),
+    csvSafe(f.patternName),
+    csvSafe(f.match),
+    csvSafe(f.type),
+    csvSafe(f.domain),
+    csvSafe(f.url),
+    csvSafe(f.pageUrl),
+    csvSafe(f.timestamp ? new Date(f.timestamp).toISOString() : ""),
   ]);
   const csv = [headers.join(","), ...rows.map((r) => r.join(","))].join("\n");
   const blob = new Blob([csv], { type: "text/csv" });

manifest.json

@@ -25,14 +25,22 @@
     },
     {
       "matches": ["<all_urls>"],
-      "js": ["js/interceptor.js"],
+      "js": ["js/interceptor-loader.js"],
       "run_at": "document_start",
-      "world": "MAIN",
       "all_frames": true
     }
   ],
+  "content_security_policy": {
+    "extension_pages": "script-src 'self'; object-src 'self'"
+  },
   "background": {
     "service_worker": "js/background.js"
   },
+  "web_accessible_resources": [
+    {
+      "resources": ["js/interceptor.js"],
+      "matches": ["<all_urls>"]
+    }
+  ],
   "permissions": ["activeTab", "storage"]
 }