SiYuan note versions prior to 3.8.4 fail to HTML-escape stored flashcard block content before embedding it into the card-manager list markup. The vulnerable endpoint /api/riff/getRiffCards returns block content that is directly assigned to innerHTML in the card item template, enabling execution of attacker-controlled scripts such as event handlers in injected HTML elements. Because the desktop Electron application runs with nodeIntegration enabled and contextIsolation disabled, an administrator opening the card manager with attacker-supplied flashcard content executes the malicious script in a privileged renderer context. This can lead to arbitrary code execution on the host system. The endpoint is protected by authentication and administrator role checks, so exploitation requires an attacker to have or gain administrator privileges and to introduce malicious flashcard content via contribution or import.

Successful exploitation allows an attacker with administrator privileges to execute arbitrary code on the host system through script execution in the Electron renderer process. This elevates the risk of full system compromise. However, the attack requires the attacker to have administrator access and to have introduced malicious flashcard content into the workspace. There is no indication of an authorization bypass or remote unauthenticated exploitation.

A fixed version of SiYuan note is available starting from version 3.8.4 that properly escapes flashcard block content before insertion into the DOM. Users should upgrade to version 3.8.4 or later to remediate this vulnerability. Since the vulnerability requires administrator interaction with malicious content, restricting administrator access and validating imported content can reduce risk until the update is applied.