SiYuan versions prior to 3.8.4 generate gutter-button markup from plain‑text Markdown that is parsed by the Lute renderer. The data-subtype attribute is not HTML‑escaped, allowing an attacker to embed entity‑encoded quotes that break the attribute value. When the markup is re‑parsed by the browser, the injected attributes such as autofocus and onfocus are added, and if the compromised gutter control receives focus the handler executes. In the Electron desktop application this results in JavaScript execution with renderer Node.js privileges, effectively permitting remote code execution on the affected machine.

SiYuan (siyuan-note:siyuan), versions up to and including 3.8.3 are affected. The fix begins with version 3.8.4.

The CVSS score of 8.6 indicates a high‑severity vulnerability. The EPSS score is not available, and the vulnerability is not listed in the CISA KEV catalog. The likely attack vector requires an attacker to supply a crafted Markdown snippet and convince a user to paste it into the application. If the user then interacts with the gutter button, the injected handler runs with full renderer Node.js privileges. The known exploit path is benign for the user to trigger, but the elevated privileges expose the system to complete compromise if the user inadvertently focuses the control.