SiYuan is a personal knowledge management system that stores documents in .sy format. Prior to release 3.6.2, an attacker can craft a block attribute value that contains a mixed HTML entity and raw special characters. When a victim imports a .sy.zip containing this malicious attribute, the value bypasses server‑side escaping, breaks out of its original HTML context and injects an event handler. On the Electron desktop client the injected JavaScript runs with full Node/Electron privileges, allowing the attacker to execute arbitrary system commands. The weakness corresponds to Unvalidated Input and Stored Cross‑Site Scripting (CWE‑79) and code injection (CWE‑94).

The vulnerability affects the Siyuan note application, version 3.6.1 and earlier, on all operating systems where the Electron desktop client runs. It is relevant to users who use the Import → SiYuan .sy.zip workflow to bring external notes into their account. The issue does not affect the web or mobile versions, only the desktop Electron build.

The Common Vulnerability Scoring System assigns a score of 8.6, indicating high severity, and the Exploit Prediction Scoring System shows a probability of less than 1 %, meaning a real exploitation attack is unlikely to be seen. Because the attack relies on a victim importing a specifically crafted note file, it is primarily a user‑interaction attack; a malicious file can be phished or delivered via social engineering to trick the victim into opening it. The vulnerability is not listed in CISA’s Known Exploited Vulnerabilities catalog, further suggesting no publicly available exploit. Nonetheless, users of the affected Electron client should treat this as a critical patch.