SiYuan CVE-2026-74902

Exploitation requires the victim to be running SiYuan before v3.7.4 and to actively drag, drop, or paste an attacker-supplied file into the editor - the malicious payload lives in the file's NAME, which must pass through the file-upload validation flow that calls insertAdjacentHTML without escaping. Limiting factors: the attack vector is local (AV:L), so the attacker must first deliver the crafted file to the victim's system or to a location the victim imports from, and passive user interaction (UI:P) is mandatory - the file must be brought into the editor by the user. No authentication to the application is required (PR:N), but there is no remote, no-interaction path; the flaw cannot be triggered against a default install without the victim performing the drag/drop/paste import action.

The vendor CVSS 4.0 score is 9.3 (critical), vector AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H with a scope change to subsequent systems (SC:H/SI:H/SA:H), reflecting the XSS-to-RCE impact. The local attack vector (AV:L) and passive user interaction (UI:P) are the key mitigating signals: this is not a remote unauthenticated internet drive-by - the attacker must get a maliciously named file to the victim, who must then drag, drop, or paste it into the editor. No EPSS score and no CISA KEV listing were provided, and there is no POC flag in the intelligence, so this reads as high-impact-but-interaction-gated rather than mass-exploited. Weighing the signals together - trivial payload construction, full OS command impact, and a plausible social-engineering delivery path - even a mid-sized municipal IT team in opole should treat this as urgent for any SiYuan deployment, but the risk is realized per-victim on file interaction rather than as automatable, wormable exploitation. Bottom line: a genuine high priority for organizations actually running SiYuan, tempered by the local vector and required user action.

An attacker sends the victim a file whose filename contains an HTML/script payload (via a shared drive, chat attachment, or synced folder) and social-engineers them into importing it. When the victim drags, drops, or pastes the file into the SiYuan editor, the unescaped filename is injected via insertAdjacentHTML, the script executes in the privileged Electron renderer, and it runs OS commands as the user. No public exploit is identified at time of analysis, but the payload is simple to construct given the described flaw.