SiYuan EUVD-2026-39126

Exploitation requires the SiYuan instance to be older than 3.7.0 and the victim to be an Administrator who has already accepted the one-time Marketplace trust consent, then opens an attacker-published Bazaar package in Settings → Marketplace and interacts with the listing (e.g., hovers, clicks, or otherwise triggers a pointer/toggle/focusin/animation/transition event) so the injected inline handler fires. Installing the package is NOT required - merely viewing and interacting with the listing is sufficient. Limiting factors: the attacker must get a malicious package published to the Bazaar marketplace, the target must be an authenticated Administrator, and the payload only executes upon the specific user interaction that fires one of the unsanitized event handlers, which is why the CVSS vector marks UI:R and AC:H.

The provided CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L, base 7.1) is internally consistent with the description: network-reachable, but high complexity and required user interaction reflect that an Administrator must first grant one-time marketplace trust consent, then open a malicious package and interact with the listing to trigger an event handler. No EPSS score, SSVC decision, KEV entry, or public POC was supplied, so the real-world exploitation signals are thin: this is a high-severity-by-impact issue (full workspace compromise) gated by meaningful preconditions, not a mass-exploitable remote bug. The high attack complexity and dependence on Administrator interaction with attacker-controlled marketplace content make this a targeted, social-engineering-flavored threat rather than a wormable one. No conflicting signals were found, but the absence of EPSS/KEV/POC data means likelihood cannot be quantified beyond the CVSS qualitative read.

A malicious author publishes a Bazaar package whose README contains a benign-looking element carrying an inline modern event handler such as onpointerover or onbeforetoggle with a JavaScript payload. An Administrator browsing Settings → Marketplace opens the package listing and moves the pointer over or interacts with the rendered content, firing the handler; the script runs in the authenticated SiYuan origin and can take full control of the workspace. No POC is publicly identified at time of analysis, and the high attack complexity reflects the need for Administrator interaction after marketplace trust consent.