VNote CVE-2026-86016

Exploitation requires the victim to open an attacker-supplied Markdown note in VNote prior to 4.3.0, where the note contains crafted YAML frontmatter metadata that is inserted via preNode.innerHTML before the protectFromXss sanitization runs. The exfiltration capability specifically depends on the Qt setting QWebEngineSettings::LocalContentCanAccessRemoteUrls being enabled (the app's default), which lets the injected script in the file:// context read reachable local note files and send them to a remote server. Limiting factors: no code executes until the user actively opens the malicious note (UI:R), and impact is scoped to files reachable from the viewer context; there is no remote code execution against a running instance without the victim opening the crafted file.

The input CVSS 3.1 vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N, base 8.2 High) describes an unauthenticated (PR:N), low-complexity stored XSS that requires user interaction (UI:R - the victim must open a malicious note) and achieves a scope change (S:C) because injected script in the file:// viewer escapes the note-rendering context to read other local files and exfiltrate them to a remote server. The source-code evidence (commit 7371efde changing preNode.innerHTML to preNode.textContent) confirms the root cause and the fix, raising confidence in the technical description. However, no EPSS score was provided, the vulnerability is NOT in CISA KEV, and no public POC is indicated - so there is no evidence of active or widespread exploitation. The UI:R requirement plus the need to socially deliver a crafted Markdown file substantially lowers real-world mass-exploitation risk compared to a drive-by network bug; this is better characterized as a targeted/social-engineering vector than an internet-wide threat. Note a tension in the vector: AV:N is assigned although exploitation fundamentally depends on a victim locally opening a delivered file in a desktop application, which is arguably closer to local delivery - treat the AV:N rating with caution. Overall: a legitimate High-severity data-exfiltration bug in a niche desktop app, but prioritize based on whether VNote is actually deployed and users handle untrusted notes, rather than the raw 8.2 alone.

An attacker crafts a Markdown note containing malicious JavaScript inside its YAML frontmatter metadata and shares it with a target (e.g., via a note repository, email, or shared drive). When the victim opens the note in VNote prior to 4.3.0, the unsanitized innerHTML assignment executes the script in the file:// viewer context, which then reads reachable local note files and transmits their contents to an attacker-controlled server. No public exploit is identified at time of analysis, but the one-line root cause is low-complexity and well-documented in the vendor commit.