diff --git a/scripts/auto-update.js b/scripts/auto-update.js
index c6b48119..52ae9d25 100644
--- a/scripts/auto-update.js
+++ b/scripts/auto-update.js
@@ -123,6 +123,12 @@ function determineInstallCwd(record, repoRoot) {
   return repoRoot;
 }
 
+// Recognized ECC package names. A repo root is only trusted to run its
+// install-apply.js if its package.json identifies it as ECC — otherwise a
+// cloned project that ships a nested `evil/{package.json,scripts/install-apply.js}`
+// could drive auto-update into executing attacker code (GHSA-hfpv-w6mp-5g95).
+const ECC_PACKAGE_NAMES = new Set(['ecc-universal', 'everything-claude-code']);
+
 function validateRepoRoot(repoRoot) {
   const normalized = path.resolve(repoRoot);
   const packageJsonPath = path.join(normalized, 'package.json');
@@ -136,6 +142,18 @@ function validateRepoRoot(repoRoot) {
     throw new Error(`Invalid ECC repo root: missing install script at ${installApplyPath}`);
   }
 
+  let pkgName = null;
+  try {
+    pkgName = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8')).name;
+  } catch {
+    throw new Error(`Invalid ECC repo root: unreadable package.json at ${packageJsonPath}`);
+  }
+  if (!ECC_PACKAGE_NAMES.has(pkgName)) {
+    throw new Error(
+      `Refusing to run install from untrusted repo root ${normalized}: package.json name '${pkgName}' is not an official ECC package.`
+    );
+  }
+
   return normalized;
 }
 
diff --git a/scripts/lib/install-lifecycle.js b/scripts/lib/install-lifecycle.js
index 4cdfffd4..53df1e3c 100644
--- a/scripts/lib/install-lifecycle.js
+++ b/scripts/lib/install-lifecycle.js
@@ -4,6 +4,7 @@ const path = require('path');
 
 const { resolveInstallPlan, loadInstallManifests } = require('./install-manifests');
 const { readInstallState, writeInstallState } = require('./install-state');
+const { assertWithinTrustedRoot } = require('./path-safety');
 const {
   createManifestInstallPlan,
 } = require('./install-executor');
@@ -309,7 +310,12 @@ function shouldRepairFromRecordedOperations(state) {
   return getManagedOperations(state).some(operation => operation.kind !== 'copy-file');
 }
 
-function executeRepairOperation(repoRoot, operation) {
+function executeRepairOperation(repoRoot, operation, trustedRoot) {
+  // Install-state is attacker-controllable; never write/delete outside the
+  // adapter-derived trusted root, regardless of what the state file claims
+  // (GHSA-hfpv-w6mp-5g95).
+  assertWithinTrustedRoot(operation.destinationPath, trustedRoot, 'repair');
+
   if (operation.kind === 'copy-file') {
     const sourcePath = resolveOperationSourcePath(repoRoot, operation);
     if (!sourcePath || !fs.existsSync(sourcePath)) {
@@ -360,7 +366,10 @@ function executeRepairOperation(repoRoot, operation) {
   throw new Error(`Unsupported repair operation kind: ${operation.kind}`);
 }
 
-function executeUninstallOperation(operation) {
+function executeUninstallOperation(operation, trustedRoot) {
+  // Confine deletes to the trusted install root (GHSA-hfpv-w6mp-5g95).
+  assertWithinTrustedRoot(operation.destinationPath, trustedRoot, 'uninstall');
+
   if (operation.kind === 'copy-file') {
     if (!fs.existsSync(operation.destinationPath)) {
       return {
@@ -1047,7 +1056,7 @@ function repairInstalledStates(options = {}) {
 
       if (repairOperations.length > 0) {
         for (const operation of repairOperations) {
-          executeRepairOperation(context.repoRoot, operation);
+          executeRepairOperation(context.repoRoot, operation, record.targetRoot);
         }
         writeInstallState(desiredPlan.installStatePath, desiredPlan.statePreview);
       } else {
@@ -1161,12 +1170,13 @@ function uninstallInstalledStates(options = {}) {
       const operations = getManagedOperations(state);
 
       for (const operation of operations) {
-        const outcome = executeUninstallOperation(operation);
+        const outcome = executeUninstallOperation(operation, record.targetRoot);
         removedPaths.push(...outcome.removedPaths);
         cleanupTargets.push(...outcome.cleanupTargets);
       }
 
       if (fs.existsSync(state.target.installStatePath)) {
+        assertWithinTrustedRoot(state.target.installStatePath, record.targetRoot, 'uninstall');
         fs.rmSync(state.target.installStatePath, { force: true });
         removedPaths.push(state.target.installStatePath);
         cleanupTargets.push(state.target.installStatePath);
diff --git a/scripts/lib/path-safety.js b/scripts/lib/path-safety.js
new file mode 100644
index 00000000..e1ad3dd1
--- /dev/null
+++ b/scripts/lib/path-safety.js
@@ -0,0 +1,84 @@
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+
+/**
+ * Path containment helpers for install-state-driven file operations.
+ *
+ * Install-state files are project-local and therefore attacker-controllable
+ * (a cloned/forked repo can ship a crafted `.cursor/ecc-install-state.json`).
+ * `repair`/`uninstall`/`auto-update` replay recorded operations, so every
+ * write/delete destination MUST be confined to the adapter-derived trusted
+ * root — never trusted from the state file itself (GHSA-hfpv-w6mp-5g95).
+ */
+
+function safeRealpath(target) {
+  try {
+    return fs.realpathSync(path.resolve(target));
+  } catch {
+    return path.resolve(target);
+  }
+}
+
+/**
+ * Canonicalize a path that may not exist yet: realpath its nearest existing
+ * ancestor, then re-append the missing tail. This defeats symlink escapes
+ * where an intermediate directory is a symlink pointing out of the root.
+ */
+function realpathNearestExisting(target) {
+  let current = path.resolve(target);
+  const tail = [];
+  while (!fs.existsSync(current)) {
+    const parent = path.dirname(current);
+    if (parent === current) {
+      break;
+    }
+    tail.unshift(path.basename(current));
+    current = parent;
+  }
+  const real = safeRealpath(current);
+  return tail.length > 0 ? path.join(real, ...tail) : real;
+}
+
+/**
+ * True when `target` resolves to `root` itself or a path beneath it, with
+ * symlinks resolved on both sides.
+ */
+function isWithinRoot(target, root) {
+  if (!root) {
+    return false;
+  }
+  const realRoot = safeRealpath(root);
+  const realTarget = realpathNearestExisting(target);
+  if (realTarget === realRoot) {
+    return true;
+  }
+  const rel = path.relative(realRoot, realTarget);
+  return rel !== '' && !rel.startsWith('..') && !path.isAbsolute(rel);
+}
+
+/**
+ * Fail-closed guard: throw unless `target` is contained within `root`.
+ * Returns the canonicalized target path on success.
+ */
+function assertWithinTrustedRoot(target, root, action = 'write') {
+  if (!target || typeof target !== 'string') {
+    throw new Error(`Refusing to ${action}: missing destination path.`);
+  }
+  if (!root) {
+    throw new Error(`Refusing to ${action} '${target}': no trusted install root resolved.`);
+  }
+  if (!isWithinRoot(target, root)) {
+    throw new Error(
+      `Refusing to ${action} outside the install root: '${target}' is not within '${root}'.`
+    );
+  }
+  return realpathNearestExisting(target);
+}
+
+module.exports = {
+  realpathNearestExisting,
+  isWithinRoot,
+  assertWithinTrustedRoot,
+};
diff --git a/tests/lib/path-safety.test.js b/tests/lib/path-safety.test.js
new file mode 100644
index 00000000..bbf38794
--- /dev/null
+++ b/tests/lib/path-safety.test.js
@@ -0,0 +1,85 @@
+'use strict';
+/**
+ * Tests for scripts/lib/path-safety.js — the install-state containment guard
+ * that fixes arbitrary file write/delete via attacker-controlled install-state
+ * (GHSA-hfpv-w6mp-5g95).
+ */
+
+const assert = require('assert');
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+
+const { assertWithinTrustedRoot, isWithinRoot } = require('../../scripts/lib/path-safety');
+
+let passed = 0;
+let failed = 0;
+
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  PASS ${name}`);
+    passed += 1;
+  } catch (error) {
+    console.log(`  FAIL ${name}`);
+    console.log(`    ${error.message}`);
+    failed += 1;
+  }
+}
+
+const root = fs.mkdtempSync(path.join(os.tmpdir(), 'path-safety-root-'));
+const outside = fs.mkdtempSync(path.join(os.tmpdir(), 'path-safety-out-'));
+
+try {
+  test('allows a path inside the trusted root', () => {
+    const p = path.join(root, '.cursor', 'rules', 'x.md');
+    // Returns the canonicalized path (symlinks like /var -> /private/var resolved).
+    assert.doesNotThrow(() => assertWithinTrustedRoot(p, root, 'repair'));
+    assert.ok(assertWithinTrustedRoot(p, root, 'repair').endsWith(path.join('.cursor', 'rules', 'x.md')));
+    assert.strictEqual(isWithinRoot(p, root), true);
+  });
+
+  test('allows the root itself', () => {
+    assert.strictEqual(isWithinRoot(root, root), true);
+  });
+
+  test('refuses an absolute path outside the root', () => {
+    const evil = path.join(outside, 'PWNED.txt');
+    assert.throws(() => assertWithinTrustedRoot(evil, root, 'repair'), /outside the install root/);
+    assert.strictEqual(isWithinRoot(evil, root), false);
+  });
+
+  test('refuses a ../ traversal escape', () => {
+    const evil = path.join(root, '..', 'escape.txt');
+    assert.throws(() => assertWithinTrustedRoot(evil, root, 'uninstall'), /outside the install root/);
+  });
+
+  test('refuses a symlinked intermediate directory that escapes the root', () => {
+    const linkDir = path.join(root, 'link');
+    try {
+      fs.symlinkSync(outside, linkDir, 'dir');
+    } catch {
+      console.log('    (symlink unsupported on this platform; skipping)');
+      return;
+    }
+    // root/link -> outside, so root/link/PWNED resolves outside the root.
+    const evil = path.join(linkDir, 'PWNED.txt');
+    assert.throws(() => assertWithinTrustedRoot(evil, root, 'repair'), /outside the install root/);
+  });
+
+  test('refuses when no trusted root is resolved', () => {
+    assert.throws(() => assertWithinTrustedRoot(path.join(root, 'x'), null, 'repair'), /no trusted install root/);
+  });
+
+  test('refuses a missing destination path', () => {
+    assert.throws(() => assertWithinTrustedRoot('', root, 'repair'), /missing destination path/);
+  });
+} finally {
+  fs.rmSync(root, { recursive: true, force: true });
+  fs.rmSync(outside, { recursive: true, force: true });
+}
+
+console.log(`\nResults: Passed: ${passed}, Failed: ${failed}`);
+if (failed > 0) {
+  process.exit(1);
+}