fix: savePage throw on relative paths

docs/api/web-contents.md

@@ -1856,7 +1856,7 @@ the cursor when dragging.
 
 #### `contents.savePage(fullPath, saveType)`
 
-* `fullPath` string - The full file path.
+* `fullPath` string - The absolute file path.
 * `saveType` string - Specify the save type.
   * `HTMLOnly` - Save only the HTML of the page.
   * `HTMLComplete` - Save complete-html page.

shell/browser/api/save_page_handler.cc

@@ -30,6 +30,12 @@ void SavePageHandler::OnDownloadCreated(content::DownloadManager* manager,
 
 bool SavePageHandler::Handle(const base::FilePath& full_path,
                              const content::SavePageType& save_type) {
+  if (!full_path.IsAbsolute()) {
+    promise_.RejectWithErrorMessage("Path must be absolute");
+    delete this;
+    return false;
+  }
+
   auto* download_manager =
       web_contents_->GetBrowserContext()->GetDownloadManager();
   download_manager->AddObserver(this);

spec-main/api-browser-window-spec.ts

@@ -3432,6 +3432,23 @@ describe('BrowserWindow module', () => {
     });
     afterEach(closeAllWindows);
 
+    it('should throw when passing relative paths', async () => {
+      const w = new BrowserWindow({ show: false });
+      await w.loadFile(path.join(fixtures, 'pages', 'save_page', 'index.html'));
+
+      await expect(
+        w.webContents.savePage('save_page.html', 'HTMLComplete')
+      ).to.eventually.be.rejectedWith('Path must be absolute');
+
+      await expect(
+        w.webContents.savePage('save_page.html', 'HTMLOnly')
+      ).to.eventually.be.rejectedWith('Path must be absolute');
+
+      await expect(
+        w.webContents.savePage('save_page.html', 'MHTML')
+      ).to.eventually.be.rejectedWith('Path must be absolute');
+    });
+
     it('should save page to disk', async () => {
       const w = new BrowserWindow({ show: false });
       await w.loadFile(path.join(fixtures, 'pages', 'save_page', 'index.html'));