SiYuan is a personal knowledge management system. Prior to version 3.6.2, a malicious website can achieve Remote Code Execution (RCE) on any desktop running SiYuan by exploiting the permissive CORS policy (Access-Control-Allow-Origin: * + Access-Control-Allow-Private-Network: true) to inject a JavaScript snippet via the API. The injected snippet executes in Electron's Node.js context with full OS access the next time the user opens SiYuan's UI. No user interaction is required beyond visiting the malicious website while SiYuan is running. This issue has been patched in version 3.6.2.

Affected: Go: github.com/siyuan-note/siyuan/kernel

### Summary

A malicious website can achieve Remote Code Execution (RCE) on any desktop running SiYuan by exploiting the permissive CORS policy (`Access-Control-Allow-Origin: *` + `Access-Control-Allow-Private-Network: true`) to inject a JavaScript snippet via the API. The injected snippet executes in Electron's Node.js context with full OS access the next time the user opens SiYuan's UI. No user interaction is required beyond visiting the malicious website while SiYuan is running.

### Details

**Vulnerable files:** - `kernel/server/serve.go`, lines 960-963 — CORS middleware - `kernel/api/snippet.go`, lines 93-128 — snippet injection endpoint

**Root cause:** The CORS middleware unconditionally sets: ``` Access-Control-Allow-Origin: * Access-Control-Allow-Credentials: true Access-Control-Allow-Private-Network: true ```

The `Access-Control-Allow-Private-Network: true` header explicitly opts into Chrome's Private Network Access specification, telling the browser that external websites are permitted to access this localhost service. Combined with `Access-Control-Allow-Origin: *`, any website on the internet can make authenticated cross-origin requests to the SiYuan API at `127.0.0.1:6806`.

The auth middleware at `kernel/model/session.go:251-280` checks the `Origin` header, but this check is bypassed because the browser sends the session cookie (set on `127.0.0.1`) along with the cross-origin request, and the server validates the cookie before reaching the Origin check for un…