fix(privacy): wipe plaintext/PII localStorage caches on logout (SEC-1/2)

Several localStorage caches held decrypted message content or user PII and
survived a normal logout, leaving residue on a shared device (the search
index was already wiped; these were not):

- cinny_scheduled_messages_v1 - decrypted IContent.body of pending sends
- cinny_recent_searches_v1     - search query text
- cinny_recent_forward_targets_v1 - recent forward contact/room graph
- cinny_recent_gifs_v1 / cinny_recent_stickers_v1 - media the user sent
- navToActivePath<userId>       - per-space last-visited room paths
- (plus the translation cache added earlier)

Add a clear function per module and a single auditable clearPlaintextCaches()
aggregator, called from both logout paths (logoutClient + the server-forced
SessionLoggedOut handler) alongside the existing session/search-index wipes.
Unit-tested.

Deliberately NOT cleared (documented in the aggregator): unsent composer
drafts and the presence status message (preserved by product decision N98);
SDK sync/crypto store + io.lotus.* account data (reminders/bookmarks/notes),
already wiped by mx.clearStores(); low-sensitivity UI/metadata residue.

The forward-targets/gifs/stickers/nav-path additions and the accurate
"not covered" documentation address findings from two review passes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/pages/client/ClientRoot.tsx

@@ -32,7 +32,7 @@ import {
   startClient,
 } from '../../../client/initMatrix';
 import { deleteSearchCacheDatabase } from '../../utils/searchCache';
-import { clearTranslationCache } from '../../state/translation';
+import { clearPlaintextCaches } from '../../state/plaintextCaches';
 import { SplashScreen } from '../../components/splash-screen';
 import { ServerConfigsLoader } from '../../components/ServerConfigsLoader';
 import { CapabilitiesProvider } from '../../hooks/useCapabilities';
@@ -163,9 +163,10 @@ const useLogoutListener = (mx?: MatrixClient) => {
       // change) — the manual logout path already does, but this path didn't, so
       // the plaintext survived on disk (and persist() makes it non-evictable).
       await deleteSearchCacheDatabase();
-      // The message-translation cache also holds decrypted plaintext — wipe it
-      // on server-forced logout too.
-      clearTranslationCache();
+      // Other localStorage caches also hold decrypted plaintext / PII
+      // (translation, scheduled messages, recent searches/forwards/gifs/
+      // stickers, nav paths) — wipe them on server-forced logout too.
+      clearPlaintextCaches(mx?.getUserId() ?? undefined);
       // Remove only the session credential keys — NOT settings, drafts, and
       // other preferences (N98). The SDK's IndexedDB stores are cleared above;
       // window.localStorage.clear() is reserved for the explicit reset path.

src/app/state/plaintextCaches.test.ts

@@ -0,0 +1,70 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+
+// These modules touch localStorage at import/runtime. Provide a minimal mock
+// that records removed keys, then import dynamically (a static import would
+// hoist above the mock).
+const removed: string[] = [];
+const store = new Map<string, string>();
+(globalThis as { localStorage?: unknown }).localStorage = {
+  getItem: (k: string) => store.get(k) ?? null,
+  setItem: (k: string, v: string) => {
+    store.set(k, v);
+  },
+  removeItem: (k: string) => {
+    removed.push(k);
+    store.delete(k);
+  },
+};
+
+const { clearPlaintextCaches } = await import('./plaintextCaches');
+
+test('clearPlaintextCaches removes every plaintext/PII localStorage key', () => {
+  store.clear();
+  store.set('cinny_translation_cache_v1', '[]');
+  store.set('cinny_scheduled_messages_v1', '{}');
+  store.set('cinny_recent_searches_v1', '[]');
+  store.set('cinny_recent_forward_targets_v1', '[]');
+  store.set('cinny_recent_gifs_v1', '[]');
+  store.set('cinny_recent_stickers_v1', '[]');
+  removed.length = 0;
+
+  clearPlaintextCaches();
+
+  for (const key of [
+    'cinny_translation_cache_v1',
+    'cinny_scheduled_messages_v1',
+    'cinny_recent_searches_v1',
+    'cinny_recent_forward_targets_v1',
+    'cinny_recent_gifs_v1',
+    'cinny_recent_stickers_v1',
+  ]) {
+    assert.ok(removed.includes(key), `${key} cleared`);
+  }
+  assert.equal(store.size, 0, 'all keys gone from store');
+});
+
+test('clearPlaintextCaches clears the per-user nav-path store only when given a userId', () => {
+  store.clear();
+  store.set('navToActivePath@me:server', '{}');
+  removed.length = 0;
+
+  clearPlaintextCaches(); // no userId -> nav path untouched
+  assert.ok(!removed.includes('navToActivePath@me:server'), 'nav path kept without userId');
+
+  clearPlaintextCaches('@me:server');
+  assert.ok(removed.includes('navToActivePath@me:server'), 'nav path cleared with userId');
+});
+
+test('clearPlaintextCaches does NOT touch drafts or session keys', () => {
+  store.clear();
+  store.set('draft-msg-!room:server', '{"body":"unsent"}');
+  store.set('cinny_session', '{"accessToken":"x"}');
+  removed.length = 0;
+
+  clearPlaintextCaches('@me:server');
+
+  assert.ok(!removed.includes('draft-msg-!room:server'), 'draft preserved (N98)');
+  assert.ok(!removed.includes('cinny_session'), 'session key not this module’s concern');
+  assert.ok(store.has('draft-msg-!room:server'));
+});

src/app/state/plaintextCaches.ts

@@ -0,0 +1,43 @@
+import { clearTranslationCache } from './translation';
+import { clearScheduledMessages } from './scheduledMessages';
+import { clearRecentSearches } from './recentSearches';
+import { clearRecentForwardTargets } from './recentForwardTargets';
+import { clearRecentGifs } from './recentGifs';
+import { clearRecentStickers } from './recentStickers';
+import { clearNavToActivePathStore } from './navToActivePath';
+
+/**
+ * Single auditable place that wipes the `localStorage` caches holding decrypted
+ * message content, sent media, or a user's messaging/nav activity. Called on
+ * logout so this residue can't survive on a shared device.
+ *
+ * Swept here:
+ * - `cinny_translation_cache_v1` — decrypted translated message text
+ * - `cinny_scheduled_messages_v1` — decrypted `IContent.body` of pending sends
+ * - `cinny_recent_searches_v1` — search query text (PII)
+ * - `cinny_recent_forward_targets_v1` — recent forward contact/room graph (PII)
+ * - `cinny_recent_gifs_v1` / `cinny_recent_stickers_v1` — media the user sent
+ * - `navToActivePath<userId>` — per-space last-visited room paths (needs userId)
+ *
+ * NOT swept here (by design):
+ * - session credential keys → `removeFallbackSession()`
+ * - the SDK sync/crypto store + all `io.lotus.*` account data (reminders,
+ *   bookmarks, user notes, status presets — themselves plaintext) → wiped by
+ *   `mx.clearStores()` on both logout paths
+ * - the opt-in encrypted-search index (IndexedDB) → `deleteSearchCacheDatabase()`
+ * - unsent composer drafts (`draft-msg-*`) and the presence status message
+ *   (`lotus-status-msg-*`) are deliberately preserved across a normal logout
+ *   (N98); clearing them is a separate product decision
+ * - low-sensitivity UI/metadata residue (`io.lotus.mute_timers`, collapsed
+ *   nav/space categories, `cinny_oidc_dynamic_clients`) is treated as
+ *   preferences, not swept here
+ */
+export const clearPlaintextCaches = (userId?: string): void => {
+  clearTranslationCache();
+  clearScheduledMessages();
+  clearRecentSearches();
+  clearRecentForwardTargets();
+  clearRecentGifs();
+  clearRecentStickers();
+  if (userId) clearNavToActivePathStore(userId);
+};

src/app/state/recentForwardTargets.ts

@@ -39,3 +39,16 @@ export const addRecentForwardTarget = (prev: string[], roomId: string): string[]
   const withoutDupe = prev.filter((id) => id !== roomId);
   return [roomId, ...withoutDupe].slice(0, MAX_RECENT_FORWARD_TARGETS);
 };
+
+/**
+ * Wipe persisted recent forward targets. Called on logout — the list is the
+ * user's recent messaging contact/room graph (PII) and must not survive a
+ * session on a shared device.
+ */
+export const clearRecentForwardTargets = (): void => {
+  try {
+    localStorage.removeItem(STORAGE_KEY);
+  } catch {
+    /* localStorage unavailable — nothing to clear */
+  }
+};

src/app/state/recentGifs.ts

@@ -48,3 +48,16 @@ export const addRecentGif = (
   const withoutDupe = prev.filter((g) => g.url !== gif.url);
   return [gif, ...withoutDupe].slice(0, max);
 };
+
+/**
+ * Wipe persisted recent GIFs. Called on logout — these are media the user sent
+ * (can be personally sensitive) and must not surface under "Recent" to the next
+ * person on a shared device.
+ */
+export const clearRecentGifs = (): void => {
+  try {
+    localStorage.removeItem(STORAGE_KEY);
+  } catch {
+    /* localStorage unavailable — nothing to clear */
+  }
+};

src/app/state/recentSearches.ts

@@ -36,3 +36,15 @@ export const addRecentSearch = (prev: string[], term: string): string[] => {
   const withoutDupe = prev.filter((t) => t !== trimmed);
   return [trimmed, ...withoutDupe].slice(0, MAX_RECENT_SEARCHES);
 };
+
+/**
+ * Wipe persisted recent search terms. Called on logout — search queries are
+ * user PII and must not survive a session on a shared device.
+ */
+export const clearRecentSearches = (): void => {
+  try {
+    localStorage.removeItem(STORAGE_KEY);
+  } catch {
+    /* localStorage unavailable — nothing to clear */
+  }
+};

src/app/state/recentStickers.ts

@@ -48,3 +48,16 @@ export const addRecentSticker = (
   const withoutDupe = prev.filter((s) => s.url !== sticker.url);
   return [sticker, ...withoutDupe].slice(0, max);
 };
+
+/**
+ * Wipe persisted recent stickers. Called on logout — these are stickers the
+ * user sent (mxc + label text) and must not surface under "Recent" to the next
+ * person on a shared device.
+ */
+export const clearRecentStickers = (): void => {
+  try {
+    localStorage.removeItem(STORAGE_KEY);
+  } catch {
+    /* localStorage unavailable — nothing to clear */
+  }
+};

src/app/state/scheduledMessages.ts

@@ -40,3 +40,16 @@ export const scheduledMessagesAtom = atom(
     });
   },
 );
+
+/**
+ * Wipe persisted scheduled messages. Called on logout — the stored content is
+ * decrypted message plaintext (the E2EE `body`), so it must not survive a
+ * session on a shared device.
+ */
+export const clearScheduledMessages = (): void => {
+  try {
+    localStorage.removeItem(STORAGE_KEY);
+  } catch {
+    /* localStorage unavailable — nothing to clear */
+  }
+};

src/client/initMatrix.ts

@@ -7,7 +7,7 @@ import { LotusOidcTokenRefresher } from './oidcTokenRefresher';
 import { revokeOidcTokens } from './oidcLogout';
 import { pushSessionToSW } from '../sw-session';
 import { deleteSearchCacheDatabase } from '../app/utils/searchCache';
-import { clearTranslationCache } from '../app/state/translation';
+import { clearPlaintextCaches } from '../app/state/plaintextCaches';
 
 // Thrown when the local IndexedDB has a higher schema version than this SDK expects.
 // This happens after a downgrade (e.g. matrix-js-sdk was briefly upgraded and then reverted).
@@ -124,8 +124,10 @@ export const logoutClient = async (mx: MatrixClient) => {
   // The opt-in local search index stores decrypted plaintext — always wipe it
   // on logout. (clearLoginData below nukes all IDB databases, covering it too.)
   await deleteSearchCacheDatabase();
-  // The message-translation cache also holds decrypted plaintext — wipe it too.
-  clearTranslationCache();
+  // Other localStorage caches also hold decrypted plaintext / PII (translation,
+  // scheduled messages, recent searches/forwards/gifs/stickers, nav paths) —
+  // wipe them too.
+  clearPlaintextCaches(mx.getUserId() ?? undefined);
   // Remove only the session credential keys, preserving user preferences and
   // unsent drafts (N98). The factory-reset path is clearLoginData() below.
   removeFallbackSession();