SiYuan’s Lute HTML sanitizer fails to strip <iframe> elements before version 3.7.0. When a malicious Bazaar package README is displayed in the Electron client, the embedded <iframe> triggers execution of arbitrary commands on the host machine. The weakness is an injection flaw classified as CWE‑79, which directly compromises confidentiality, integrity, and availability of the affected system.

The affected product is Siyuan by siyuan-note. Any deployment of the Siyuan client running a version earlier than 3.7.0 is vulnerable. The Electron-based desktop application is the primary entry point, as it renders the README with a permissive security configuration.

The CVSS score of 8.7 indicates high severity. No EPSS score is publicly available, and the vulnerability is not listed in the CISA KEV catalog. An attacker can introduce a malicious README into a Bazaar package distributed to a user; the README is rendered automatically when the package details are viewed, so no explicit installation of the package is required. The attack vector is likely local or social‑engineering based, relying on user interaction to open the README. Timely remediation is essential to prevent exploitation.