SiYuan renders notification messages as raw HTML inside an Electron window. The message posting API accepts a user-controlled value and forwards it to the renderer using insertAdjacentHTML. Because the Electron application is configured with nodeIntegration: true, contextIsolation: false, and webSecurity: false, any JavaScript executed from a notification gains unrestricted access to the Node.js API, allowing it to run arbitrary code on the host. The flaw is therefore a classic cross‑site scripting that is upgraded to local code execution on the desktop client.

The vulnerability affects all SiYuan note desktop builds before version 3.6.5; the fix was introduced in 3.6.5 and later. Users running any earlier release of SiYuan on Windows, macOS, or Linux are potentially exposed.

The CVSS score of 8.8 indicates a high‑impact flaw, but the EPSS score of less than 1% suggests that exploit activity is currently minimal. The vulnerability is not listed in the CISA KEV catalog. An attacker must be able to send a crafted notification to the local instance, either by exploiting a local API or by gaining access to the same network or user account that can publish notifications. Once the notification is displayed, the attacker can execute arbitrary code with the privileges of the application user.