diff --git a/package.json b/package.json
index a236f19..5715e06 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "real-debrid-downloader",
-  "version": "1.4.17",
+  "version": "1.4.18",
   "description": "Real-Debrid Downloader Desktop (Electron + React + TypeScript)",
   "main": "build/main/main/main.js",
   "author": "Sucukdeluxe",
diff --git a/src/main/cleanup.ts b/src/main/cleanup.ts
index 265f89e..067e418 100644
--- a/src/main/cleanup.ts
+++ b/src/main/cleanup.ts
@@ -110,8 +110,11 @@ export function removeDownloadLinkArtifacts(extractDir: string): number {
       if (!shouldDelete && [".txt", ".html", ".htm", ".nfo"].includes(ext)) {
         if (/[._\- ](links?|downloads?|urls?|dlc)([._\- ]|$)/i.test(name)) {
           try {
-            const text = fs.readFileSync(full, "utf8");
-            shouldDelete = /https?:\/\//i.test(text);
+            const stat = fs.statSync(full);
+            if (stat.size <= 256 * 1024) {
+              const text = fs.readFileSync(full, "utf8");
+              shouldDelete = /https?:\/\//i.test(text);
+            }
           } catch {
             shouldDelete = false;
           }
diff --git a/src/main/download-manager.ts b/src/main/download-manager.ts
index b4863b8..92c3fc6 100644
--- a/src/main/download-manager.ts
+++ b/src/main/download-manager.ts
@@ -76,7 +76,21 @@ type DownloadManagerOptions = {
 };
 
 function cloneSession(session: SessionState): SessionState {
-  return JSON.parse(JSON.stringify(session)) as SessionState;
+  const clonedItems: Record<string, DownloadItem> = {};
+  for (const key of Object.keys(session.items)) {
+    clonedItems[key] = { ...session.items[key] };
+  }
+  const clonedPackages: Record<string, PackageEntry> = {};
+  for (const key of Object.keys(session.packages)) {
+    const pkg = session.packages[key];
+    clonedPackages[key] = { ...pkg, itemIds: [...pkg.itemIds] };
+  }
+  return {
+    ...session,
+    packageOrder: [...session.packageOrder],
+    packages: clonedPackages,
+    items: clonedItems
+  };
 }
 
 function parseContentRangeTotal(contentRange: string | null): number | null {
@@ -1605,6 +1619,8 @@ export class DownloadManager extends EventEmitter {
     }
     delete this.session.packages[packageId];
     this.session.packageOrder = this.session.packageOrder.filter((id) => id !== packageId);
+    this.runPackageIds.delete(packageId);
+    this.runCompletedPackages.delete(packageId);
   }
 
   private async ensureScheduler(): Promise<void> {
@@ -2120,7 +2136,13 @@ export class DownloadManager extends EventEmitter {
     let lastError = "";
     let effectiveTargetPath = targetPath;
     for (let attempt = 1; attempt <= REQUEST_RETRIES; attempt += 1) {
-      const existingBytes = fs.existsSync(effectiveTargetPath) ? fs.statSync(effectiveTargetPath).size : 0;
+      let existingBytes = 0;
+      try {
+        const stat = await fs.promises.stat(effectiveTargetPath);
+        existingBytes = stat.size;
+      } catch {
+        // file does not exist
+      }
       const headers: Record<string, string> = {};
       if (existingBytes > 0) {
         headers.Range = `bytes=${existingBytes}-`;
@@ -2884,13 +2906,7 @@ export class DownloadManager extends EventEmitter {
       return;
     }
 
-    for (const itemId of pkg.itemIds) {
-      delete this.session.items[itemId];
-    }
-    delete this.session.packages[packageId];
-    this.session.packageOrder = this.session.packageOrder.filter((id) => id !== packageId);
-    this.runPackageIds.delete(packageId);
-    this.runCompletedPackages.delete(packageId);
+    this.removePackageFromSession(packageId, [...pkg.itemIds]);
   }
 
   private applyCompletedCleanupPolicy(packageId: string, itemId: string): void {
@@ -2907,29 +2923,21 @@ export class DownloadManager extends EventEmitter {
     if (policy === "immediate") {
       pkg.itemIds = pkg.itemIds.filter((id) => id !== itemId);
       delete this.session.items[itemId];
+      if (pkg.itemIds.length === 0) {
+        this.removePackageFromSession(packageId, []);
+      }
+      return;
     }
 
     if (policy === "package_done") {
       const hasOpen = pkg.itemIds.some((id) => {
         const item = this.session.items[id];
-        if (!item) {
-          return false;
-        }
-        return item.status !== "completed";
+        return item != null && item.status !== "completed";
       });
       if (!hasOpen) {
-        for (const id of pkg.itemIds) {
-          delete this.session.items[id];
-        }
-        delete this.session.packages[packageId];
-        this.session.packageOrder = this.session.packageOrder.filter((id) => id !== packageId);
+        this.removePackageFromSession(packageId, [...pkg.itemIds]);
       }
     }
-
-    if (pkg.itemIds.length === 0) {
-      delete this.session.packages[packageId];
-      this.session.packageOrder = this.session.packageOrder.filter((id) => id !== packageId);
-    }
   }
 
   private finishRun(): void {
diff --git a/src/main/extractor.ts b/src/main/extractor.ts
index 56ca0ec..cf44385 100644
--- a/src/main/extractor.ts
+++ b/src/main/extractor.ts
@@ -936,7 +936,7 @@ export async function extractPackageArchives(options: ExtractOptions): Promise<{
             extractZipArchive(archivePath, options.targetDir, options.conflictMode);
             archivePercent = 100;
           } catch {
-            const usedPassword = await runExternalExtract(archivePath, options.targetDir, options.conflictMode, passwordCandidates, (value) => {
+            const usedPassword = await runExternalExtract(archivePath, options.targetDir, "overwrite", passwordCandidates, (value) => {
               archivePercent = Math.max(archivePercent, value);
               emitProgress(extracted + failed, archiveName, "extracting", archivePercent, Date.now() - archiveStartedAt);
             }, options.signal);
diff --git a/src/main/integrity.ts b/src/main/integrity.ts
index 5489050..697925a 100644
--- a/src/main/integrity.ts
+++ b/src/main/integrity.ts
@@ -52,6 +52,10 @@ export function readHashManifest(packageDir: string): Map<string, ParsedHashEntr
     const filePath = path.join(packageDir, entry.name);
     let lines: string[];
     try {
+      const stat = fs.statSync(filePath);
+      if (stat.size > 5 * 1024 * 1024) {
+        continue;
+      }
       lines = fs.readFileSync(filePath, "utf8").split(/\r?\n/);
     } catch {
       continue;
diff --git a/src/main/storage.ts b/src/main/storage.ts
index c857e1e..8f8cd5d 100644
--- a/src/main/storage.ts
+++ b/src/main/storage.ts
@@ -158,13 +158,26 @@ export function loadSettings(paths: StoragePaths): AppSettings {
   }
 }
 
+function syncRenameWithExdevFallback(tempPath: string, targetPath: string): void {
+  try {
+    fs.renameSync(tempPath, targetPath);
+  } catch (renameError: unknown) {
+    if ((renameError as NodeJS.ErrnoException).code === "EXDEV") {
+      fs.copyFileSync(tempPath, targetPath);
+      try { fs.rmSync(tempPath, { force: true }); } catch {}
+    } else {
+      throw renameError;
+    }
+  }
+}
+
 export function saveSettings(paths: StoragePaths, settings: AppSettings): void {
   ensureBaseDir(paths.baseDir);
   const persisted = sanitizeCredentialPersistence(normalizeSettings(settings));
   const payload = JSON.stringify(persisted, null, 2);
   const tempPath = `${paths.configFile}.tmp`;
   fs.writeFileSync(tempPath, payload, "utf8");
-  fs.renameSync(tempPath, paths.configFile);
+  syncRenameWithExdevFallback(tempPath, paths.configFile);
 }
 
 export function emptySession(): SessionState {
@@ -209,7 +222,7 @@ export function saveSession(paths: StoragePaths, session: SessionState): void {
   const payload = JSON.stringify({ ...session, updatedAt: Date.now() });
   const tempPath = `${paths.sessionFile}.tmp`;
   fs.writeFileSync(tempPath, payload, "utf8");
-  fs.renameSync(tempPath, paths.sessionFile);
+  syncRenameWithExdevFallback(tempPath, paths.sessionFile);
 }
 
 let asyncSaveRunning = false;
diff --git a/src/main/utils.ts b/src/main/utils.ts
index da4e094..11d6eaa 100644
--- a/src/main/utils.ts
+++ b/src/main/utils.ts
@@ -21,7 +21,7 @@ export function compactErrorText(message: unknown, maxLen = 220): string {
 }
 
 export function sanitizeFilename(name: string): string {
-  const cleaned = String(name || "").trim().replace(/[\\/:*?"<>|]/g, " ").replace(/\s+/g, " ").trim();
+  const cleaned = String(name || "").trim().replace(/\0/g, "").replace(/[\\/:*?"<>|]/g, " ").replace(/\s+/g, " ").trim();
   return cleaned || "Paket";
 }
 
diff --git a/tests/extractor.test.ts b/tests/extractor.test.ts
index 190e604..b54748d 100644
--- a/tests/extractor.test.ts
+++ b/tests/extractor.test.ts
@@ -421,4 +421,30 @@ describe("extractor", () => {
     expect(result.failed).toBe(0);
     expect(result.extracted).toBe(0);
   });
+
+  it("rejects zip entries with path traversal", async () => {
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), "rd-extract-"));
+    tempDirs.push(root);
+    const packageDir = path.join(root, "pkg");
+    const targetDir = path.join(root, "out");
+    fs.mkdirSync(packageDir, { recursive: true });
+
+    const zip = new AdmZip();
+    zip.addFile("safe.txt", Buffer.from("safe"));
+    zip.addFile("../escaped.txt", Buffer.from("malicious"));
+    zip.writeZip(path.join(packageDir, "traversal.zip"));
+
+    const result = await extractPackageArchives({
+      packageDir,
+      targetDir,
+      cleanupMode: "none",
+      conflictMode: "overwrite",
+      removeLinks: false,
+      removeSamples: false
+    });
+
+    expect(result.extracted).toBe(1);
+    expect(fs.existsSync(path.join(targetDir, "safe.txt"))).toBe(true);
+    expect(fs.existsSync(path.join(root, "escaped.txt"))).toBe(false);
+  });
 });
diff --git a/tests/utils.test.ts b/tests/utils.test.ts
index cc163fc..dbeb437 100644
--- a/tests/utils.test.ts
+++ b/tests/utils.test.ts
@@ -12,6 +12,8 @@ describe("utils", () => {
   it("sanitizes filenames", () => {
     expect(sanitizeFilename("foo/bar:baz*")).toBe("foo bar baz");
     expect(sanitizeFilename("   ")).toBe("Paket");
+    expect(sanitizeFilename("test\0file.txt")).toBe("testfile.txt");
+    expect(sanitizeFilename("\0\0\0")).toBe("Paket");
   });
 
   it("parses package markers", () => {