diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index ce1d6e9..0bf39ee 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -10,6 +10,7 @@ export enum VerifyErrorCode {
   KEY_FETCH_FAILED = "KEY_FETCH_FAILED",
   MISSING_MANIFEST = "MISSING_MANIFEST",
   MISSING_FILE = "MISSING_FILE",
+  UNEXPECTED_FILE = "UNEXPECTED_FILE",
   HASH_MISMATCH = "HASH_MISMATCH",
   INVALID_FRONT_MATTER = "INVALID_FRONT_MATTER",
   NETWORK_ERROR = "NETWORK_ERROR",
diff --git a/packages/core/src/verify.ts b/packages/core/src/verify.ts
index a49f0e3..2bb90bb 100644
--- a/packages/core/src/verify.ts
+++ b/packages/core/src/verify.ts
@@ -129,6 +129,21 @@ async function sha256Hex(data: Uint8Array): Promise<string> {
     .join("");
 }
 
+function findUnexpectedFiles(
+  manifest: PackageManifest,
+  files: Map<string, Uint8Array>,
+): FileIntegrityResult[] {
+  const allowed = new Set(Object.keys(manifest.files));
+  const extras: FileIntegrityResult[] = [];
+  for (const path of files.keys()) {
+    if (path === "MANIFEST.json") continue;
+    if (!allowed.has(path)) {
+      extras.push({ path, valid: false, code: VerifyErrorCode.UNEXPECTED_FILE });
+    }
+  }
+  return extras;
+}
+
 async function verifyManifestHashes(
   manifest: PackageManifest,
   files: Map<string, Uint8Array>,
@@ -235,16 +250,15 @@ export async function verifyPackage(
     };
   }
 
-  const fileResults = await verifyManifestHashes(manifest, files);
+  const extras = findUnexpectedFiles(manifest, files);
+  const fileResults = [...(await verifyManifestHashes(manifest, files)), ...extras];
   const hasFailedFile = fileResults.some((f) => !f.valid);
   if (hasFailedFile) {
     const firstFailed = fileResults.find((f) => !f.valid)!;
     return {
       valid: false,
       code: firstFailed.code,
-      reason: firstFailed.code === VerifyErrorCode.MISSING_FILE
-        ? `Missing file: ${firstFailed.path}`
-        : `Hash mismatch for file: ${firstFailed.path}`,
+      reason: failedFileReason(firstFailed),
       details: { ...docMeta(manifest), signers, files: fileResults },
     };
   }
@@ -255,6 +269,14 @@ export async function verifyPackage(
   };
 }
 
+function failedFileReason(f: FileIntegrityResult): string {
+  switch (f.code) {
+    case VerifyErrorCode.MISSING_FILE: return `Missing file: ${f.path}`;
+    case VerifyErrorCode.UNEXPECTED_FILE: return `Unexpected file not in manifest: ${f.path}`;
+    default: return `Hash mismatch for file: ${f.path}`;
+  }
+}
+
 // -- DNS TXT ------------------------------------------------------------------
 
 export function parseDnsTxtRecord(txt: string): DnsTxtKeyRecord | null {
@@ -709,16 +731,15 @@ async function verifyZipFromAuthor(
     files.set(path, data);
   }
 
-  const fileResults = await verifyManifestHashes(manifest, files);
+  const extras = findUnexpectedFiles(manifest, files);
+  const fileResults = [...(await verifyManifestHashes(manifest, files)), ...extras];
   const hasFailedFile = fileResults.some((f) => !f.valid);
   if (hasFailedFile) {
     const firstFailed = fileResults.find((f) => !f.valid)!;
     return {
       valid: false,
       code: firstFailed.code,
-      reason: firstFailed.code === VerifyErrorCode.MISSING_FILE
-        ? `Missing file: ${firstFailed.path}`
-        : `Hash mismatch for file: ${firstFailed.path}`,
+      reason: failedFileReason(firstFailed),
       details: { ...docMeta(manifest), signers, files: fileResults },
     };
   }
diff --git a/packages/core/test/verify.spec.ts b/packages/core/test/verify.spec.ts
index 956e620..ff45ff6 100644
--- a/packages/core/test/verify.spec.ts
+++ b/packages/core/test/verify.spec.ts
@@ -202,6 +202,21 @@ describe("verifyPackage", () => {
     expect(result.details?.signers![0].code).toBe(VerifyErrorCode.MALFORMED_SIGNATURE);
   });
 
+  it("rejects ZIP with extra unsigned file not in manifest", async () => {
+    const { publicKey, privateKey } = await generateKeyPair();
+    const zip = zipSync({ "safe.txt": enc("safe content") });
+    const signed = await signPackage(zip, PKG_META, privateKey);
+    const entries = unzipSync(signed);
+    entries["evil.sh"] = enc("#!/bin/bash\nmalicious");
+    const tampered = zipSync(entries);
+    const result = await verifyPackage(tampered, publicKey);
+    expect(result.valid).toBe(false);
+    expect(result.code).toBe(VerifyErrorCode.UNEXPECTED_FILE);
+    const extra = result.details?.files!.find((f) => f.path === "evil.sh");
+    expect(extra?.valid).toBe(false);
+    expect(extra?.code).toBe(VerifyErrorCode.UNEXPECTED_FILE);
+  });
+
   it("verifies package with multiple files", async () => {
     const { publicKey, privateKey } = await generateKeyPair();
     const zip = zipSync({
@@ -455,6 +470,29 @@ signatures:
     expect(result.code).toBe(VerifyErrorCode.NO_SIGNATURES);
   });
 
+  it("rejects ZIP with extra unsigned file via verifyFromAuthor (UNEXPECTED_FILE)", async () => {
+    const { privateKey, publicKey } = await generateKeyPair();
+    const zip = zipSync({ "safe.txt": enc("safe content") });
+    const signed = await signPackage(zip, PKG_META, privateKey);
+    const entries = unzipSync(signed);
+    entries["evil.sh"] = enc("#!/bin/bash\nmalicious");
+    const tampered = zipSync(entries);
+
+    const pubKeyB64 = uint8ToBase64(publicKey);
+    const futureDate = new Date("2030-01-01T00:00:00Z").toISOString();
+    const result = await verifyFromAuthor(tampered, {
+      fetch: mockFetchWithKeys([
+        { keyId: "key_test", algorithm: "ed25519", publicKey: pubKeyB64, expires: futureDate },
+      ]) as typeof globalThis.fetch,
+      resolveTxt: false,
+    });
+    expect(result.valid).toBe(false);
+    expect(result.code).toBe(VerifyErrorCode.UNEXPECTED_FILE);
+    const extra = result.details?.files!.find((f) => f.path === "evil.sh");
+    expect(extra?.valid).toBe(false);
+    expect(extra?.code).toBe(VerifyErrorCode.UNEXPECTED_FILE);
+  });
+
   it("rejects revoked HTTPS key even when DNS reports it valid (no race bypass)", async () => {
     const { privateKey, publicKey } = await generateKeyPair();
     const signed = await signFile(SAMPLE_MD, privateKey, { keyId: "key_test", publisher: "example.com" });