diff --git a/src/extract.ts b/src/extract.ts
index fe42f75..07c4472 100644
--- a/src/extract.ts
+++ b/src/extract.ts
@@ -9,6 +9,7 @@ import { unzipSync } from "fflate";
 
 const ZIP_SIGNATURE = Buffer.from([0x50, 0x4b, 0x03, 0x04]);
 const MAX_TOTAL_BYTES = 200 * 1024 * 1024;
+const MAX_ENTRIES = 2000;
 
 export function isZip(bytes: Buffer): boolean {
   return bytes.length >= 4 && bytes.subarray(0, 4).equals(ZIP_SIGNATURE);
@@ -37,9 +38,16 @@ export function isSafeEntryPath(name: string): boolean {
 export function extractZip(bytes: Buffer, targetDir: string): string[] {
   // A szűrő a kibontás ELŐTT fut, a központi jegyzék `originalSize` mezőjéből:
   // egy apró, erősen tömörített zip így nem tudja kimeríteni a memóriát.
+  // A lemezre írás csak a teljes szűrés után történik, így ha valamelyik
+  // korlát hibát dob, semmi nem kerül a célmappába.
   let total = 0;
+  let entryCount = 0;
   const entries = unzipSync(new Uint8Array(bytes), {
     filter(info) {
+      entryCount += 1;
+      if (entryCount > MAX_ENTRIES) {
+        throw new Error("A zip bejegyzésszáma meghaladja a 2000-es korlátot.");
+      }
       if (info.name.endsWith("/")) {
         return false;
       }
@@ -58,8 +66,8 @@ export function extractZip(bytes: Buffer, targetDir: string): string[] {
   for (const [name, data] of Object.entries(entries)) {
     const relative = name.replace(/\\/g, "/").split(posix.sep).join(sep);
     const target = join(targetDir, relative);
-    mkdirSync(dirname(target), { recursive: true });
-    writeFileSync(target, data);
+    mkdirSync(dirname(target), { recursive: true, mode: 0o700 });
+    writeFileSync(target, data, { mode: 0o600 });
     written.push(relative);
   }
 
diff --git a/src/store/index.ts b/src/store/index.ts
index 5dd5d69..6a57eb8 100644
--- a/src/store/index.ts
+++ b/src/store/index.ts
@@ -40,6 +40,11 @@ export function knownIds(entries: readonly IndexEntry[]): Set<string> {
 }
 
 export function appendIndex(outDir: string, entry: IndexEntry): void {
-  mkdirSync(outDir, { recursive: true });
-  appendFileSync(join(outDir, INDEX_FILE), `${JSON.stringify(entry)}\n`, "utf8");
+  mkdirSync(outDir, { recursive: true, mode: 0o700 });
+  // A `mode` csak a fájl létrehozásakor érvényesül: a meglévő index.jsonl
+  // jogosultságait a későbbi hozzáfűzések nem bántják.
+  appendFileSync(join(outDir, INDEX_FILE), `${JSON.stringify(entry)}\n`, {
+    encoding: "utf8",
+    mode: 0o600
+  });
 }
diff --git a/src/tarhely/inbox.ts b/src/tarhely/inbox.ts
index a86c2ca..3fdbb91 100644
--- a/src/tarhely/inbox.ts
+++ b/src/tarhely/inbox.ts
@@ -152,8 +152,9 @@ async function downloadOne(
   const label = slugify(row.desc || row.type || "level").slice(0, 40);
   const dir = join(mailbox.slug, `${row.receivedOn || "ismeretlen-datum"}_${eid}_${label}`);
   const absolute = join(options.outDir, dir);
-  mkdirSync(absolute, { recursive: true });
-  writeFileSync(join(absolute, file.name), file.bytes);
+  // A hivatalos iratokat tartalmazó mappa csak a tulajdonos számára érhető el.
+  mkdirSync(absolute, { recursive: true, mode: 0o700 });
+  writeFileSync(join(absolute, file.name), file.bytes, { mode: 0o600 });
 
   const extracted =
     options.extract && isZip(file.bytes) ? extractZip(file.bytes, join(absolute, "kibontva")) : [];
@@ -173,6 +174,9 @@ async function downloadOne(
     extracted: extracted.map((name) => join("kibontva", name)),
     downloadedAt: now().toISOString()
   };
-  writeFileSync(join(absolute, "meta.json"), `${JSON.stringify(entry, null, 2)}\n`, "utf8");
+  writeFileSync(join(absolute, "meta.json"), `${JSON.stringify(entry, null, 2)}\n`, {
+    encoding: "utf8",
+    mode: 0o600
+  });
   return entry;
 }
diff --git a/test/browser.test.ts b/test/browser.test.ts
index 5e8343d..bb31f86 100644
--- a/test/browser.test.ts
+++ b/test/browser.test.ts
@@ -50,6 +50,40 @@ describe("isAllowedHost", () => {
     expect(isAllowedHost("not-tarhely.gov.hu")).toBe(false);
   });
 
+  it("allows uppercase host because URL parsing normalizes it to lowercase", () => {
+    const host = new URL("https://KAU.GOV.HU/").hostname;
+    expect(host).toBe("kau.gov.hu");
+    expect(isAllowedHost(host)).toBe(true);
+  });
+
+  it("rejects host with trailing dot", () => {
+    expect(isAllowedHost("kau.gov.hu.")).toBe(false);
+  });
+
+  it("rejects Cyrillic homoglyph host and its punycode form", () => {
+    // A második betű cirill á (U+0430), nem latin a.
+    const homoglyph = "kаu.gov.hu";
+    expect(isAllowedHost(homoglyph)).toBe(false);
+    const punycode = new URL(`https://${homoglyph}/`).hostname;
+    expect(punycode).toBe("xn--ku-7kc.gov.hu");
+    expect(isAllowedHost(punycode)).toBe(false);
+  });
+
+  it("rejects host behind userinfo in URL", () => {
+    const host = new URL("https://kau.gov.hu@evil.example/").hostname;
+    expect(host).toBe("evil.example");
+    expect(isAllowedHost(host)).toBe(false);
+  });
+
+  it("rejects IPv4 address host", () => {
+    expect(isAllowedHost("192.0.2.1")).toBe(false);
+  });
+
+  it("rejects IPv6 address host", () => {
+    expect(isAllowedHost("[::1]")).toBe(false);
+    expect(isAllowedHost("::1")).toBe(false);
+  });
+
   it("supports custom allowlist patterns", () => {
     expect(isAllowedHost("api.pelda.hu", ["*.pelda.hu"])).toBe(true);
   });
diff --git a/test/extract.test.ts b/test/extract.test.ts
index 1173db5..52d9af8 100644
--- a/test/extract.test.ts
+++ b/test/extract.test.ts
@@ -65,6 +65,14 @@ describe("isSafeEntryPath", () => {
   });
 });
 
+function buildManyEntryZip(entryCount: number): Buffer {
+  const files: Record<string, Uint8Array> = {};
+  for (let index = 0; index < entryCount; index++) {
+    files[`bejegyzes-${index}.txt`] = new Uint8Array(0);
+  }
+  return Buffer.from(zipSync(files));
+}
+
 describe("extractZip", () => {
   it("extracts zip entries to target directory and returns relative paths", () => {
     const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-test-"));
@@ -109,4 +117,35 @@ describe("extractZip", () => {
     );
     expect(() => extractZip(zipData, tmpDir)).toThrow("Gyanús útvonal a zipben");
   });
+
+  it("throws when the zip contains more than 2000 entries and writes no files", () => {
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-test-"));
+    const zipData = buildManyEntryZip(2001);
+    expect(() => extractZip(zipData, tmpDir)).toThrow(
+      "A zip bejegyzésszáma meghaladja a 2000-es korlátot."
+    );
+    expect(fs.readdirSync(tmpDir)).toEqual([]);
+  });
+
+  it("extracts a zip with exactly 2000 entries", () => {
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-test-"));
+    const zipData = buildManyEntryZip(2000);
+    const written = extractZip(zipData, tmpDir);
+    expect(written).toHaveLength(2000);
+  });
+
+  it.skipIf(process.platform === "win32")(
+    "creates directories with 0o700 mode and extracted files with 0o600 mode",
+    () => {
+      const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-test-"));
+      const zipData = Buffer.from(
+        zipSync({
+          "almappa/irat.pdf": Buffer.from("tartalom")
+        })
+      );
+      extractZip(zipData, tmpDir);
+      expect(fs.statSync(path.join(tmpDir, "almappa")).mode & 0o777).toBe(0o700);
+      expect(fs.statSync(path.join(tmpDir, "almappa", "irat.pdf")).mode & 0o777).toBe(0o600);
+    }
+  );
 });
diff --git a/test/inbox.test.ts b/test/inbox.test.ts
index 1c28e07..bf49692 100644
--- a/test/inbox.test.ts
+++ b/test/inbox.test.ts
@@ -300,6 +300,28 @@ describe("downloadNewLetters", () => {
     expect(readIndex(outDir)).toHaveLength(2);
   });
 
+  // A jogosultsági bitek Windowson nincsenek értelmezve, ott a teszt nem fut.
+  // A 022 umask nem maszkolja a 0o700/0o600 módokat, ezért pontos egyenlőség várható.
+  it.skipIf(process.platform === "win32")(
+    "creates the letter directory with 0o700 and the letter file and meta.json with 0o600",
+    async () => {
+      const outDir = tempOutDir();
+      const harness = createHarness(
+        [rawRow({ eid: EID_0101, receivedAtMs: Date.UTC(2026, 0, 1, 10) })],
+        { [EID_0101]: { fajlNev: "level-1.pdf" } },
+        { [EID_0101]: Buffer.from("pdf-tartalom-1") }
+      );
+
+      const result = await runDownload(harness, outDir);
+      expect(result.downloaded).toBe(1);
+
+      const dir = letterDir(outDir, EID_0101, "2026-01-01");
+      expect(fs.statSync(dir).mode & 0o777).toBe(0o700);
+      expect(fs.statSync(path.join(dir, "level-1.pdf")).mode & 0o777).toBe(0o600);
+      expect(fs.statSync(path.join(dir, "meta.json")).mode & 0o777).toBe(0o600);
+    }
+  );
+
   it("keeps downloading when one letter fails, reports it, keeps it out of index.jsonl and retries it on the next run", async () => {
     const outDir = tempOutDir();
     const harness = createHarness(
diff --git a/test/index-store.test.ts b/test/index-store.test.ts
index 4e5d089..924133b 100644
--- a/test/index-store.test.ts
+++ b/test/index-store.test.ts
@@ -72,6 +72,18 @@ describe("appendIndex", () => {
     expect(readIndex(tmpDir)).toEqual([sampleEntry1]);
   });
 
+  // A jogosultsági bitek Windowson nincsenek értelmezve, ott a teszt nem fut.
+  // A 022 umask nem maszkolja a 0o700/0o600 módokat, ezért pontos egyenlőség várható.
+  it.skipIf(process.platform === "win32")(
+    "creates the outDir with 0o700 and index.jsonl with 0o600 permissions",
+    () => {
+      const tmpDir = path.join(fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-idx-")), "submappa");
+      appendIndex(tmpDir, sampleEntry1);
+      expect(fs.statSync(tmpDir).mode & 0o777).toBe(0o700);
+      expect(fs.statSync(path.join(tmpDir, INDEX_FILE)).mode & 0o777).toBe(0o600);
+    }
+  );
+
   it("appends multiple entries in order", () => {
     const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-idx-"));
     appendIndex(tmpDir, sampleEntry1);