CVE-2026-93922: SiYuan Stored XSS Risk

How to Detect CVE-2026-93922

Detection should combine application inventory, notebook metadata review, endpoint telemetry, and user reports.

First, identify SiYuan installations and confirm whether any run version 3.8.4 or earlier. Next, review notebook names for:

• Suspicious HTML elements
• Event handlers
• Script fragments
• Encoded JavaScript
• References to local process execution
• Unexpected external URLs

Such content is not by itself proof of exploitation, but it can identify malicious input requiring containment.

Endpoint monitoring is particularly important because the described impact may extend beyond the application. Look for SiYuan or its Electron helper processes spawning shells, scripting engines, interpreters, download utilities, or unexpected child processes. Also investigate:

• File modifications
• Credential-store access
• Persistence changes
• New scheduled tasks or services
• Outbound connections shortly after the Daily Note picker is opened
• Unexpected access to sensitive user files

For personal endpoints, reputable endpoint security software such as Get Malwarebytes → may help identify suspicious child processes or malicious files. Endpoint protection is a supplemental control and does not patch the SiYuan vulnerability.

Technical Detection Notes

A generic process-creation query can identify suspicious descendants of SiYuan. Adapt executable names and field names to the EDR or SIEM in use:

process.parent.name IN ("siyuan", "SiYuan", "siyuan.exe")
AND process.name IN (
  "cmd.exe", "powershell.exe", "pwsh.exe", "bash", "sh",
  "zsh", "python", "python3", "curl", "wget", "osascript"
)

On Linux systems using auditd, a temporary rule can help identify process execution by the SiYuan account or binary. Replace the path with the actual installation location:

sudo auditctl -a always,exit -F arch=b64 \
  -S execve -F exe=/opt/SiYuan/siyuan -k siyuan_process
sudo ausearch -k siyuan_process -i

A useful investigation pattern is a SiYuan process followed by a shell or scripting interpreter within a short time window. Also search endpoint telemetry for command lines containing:

• -c
• -Command
• -EncodedCommand
• curl
• wget
• References to newly created files

These indicators are behavioral heuristics, not definitive signatures for CVE-2026-93922.

Mitigation and Patching

The affected range is SiYuan through 3.8.4, and the available data does not provide a verified fixed release number. Upgrade to the first version explicitly identified as fixed by the SiYuan security advisory or release notes. Do not claim that an arbitrary newer release resolves the issue without vendor confirmation.

Until a verified fix is available:

1. Prevent untrusted users from creating or modifying notebook names.
2. Review existing notebook names for HTML and JavaScript payloads.
3. Avoid opening the Daily Note picker against untrusted workspaces.
4. Isolate affected endpoints from sensitive systems where practical.
5. Monitor SiYuan for unexpected child-process creation.
6. Restrict access to shared notebooks and synchronization locations.
7. Treat imported backups and workspaces as untrusted until reviewed.

These controls reduce exposure but do not remove the vulnerability.

If exploitation is suspected, preserve endpoint and application evidence before deleting suspicious notebook names. Quarantine the affected host when appropriate, identify the operating-system account running SiYuan, review child-process activity and file changes, and rotate credentials that may have been accessible to that account. Use a reputable password manager, such as Try 1Password →, to generate and store replacement credentials where appropriate.

Technical Patching Notes

After the vendor confirms a fixed version, use the project’s documented installation method. For a package or binary deployment, the operational procedure should resemble the following, with <FIXED_VERSION> replaced only after verification:

# Record the current version and stop the application
siyuan --version
sudo systemctl stop siyuan

# Install the vendor-confirmed fixed release
# Use the official SiYuan package, updater, or release artifact.
sudo install -m 0755 ./siyuan-<FIXED_VERSION> /usr/local/bin/siyuan

sudo systemctl start siyuan
siyuan --version

Do not execute this example with an unverified version number. For desktop deployments, use the official SiYuan updater or release package and verify that the installed version is at or above the vendor-confirmed fixed release.

The immediate workaround is administrative rather than a configuration toggle: restrict notebook-name modification to trusted users, segregate shared workspaces, and avoid rendering untrusted notebooks in the Daily Note picker. Because the vulnerable behavior is an application rendering flaw, network filtering alone is unlikely to provide complete protection for a locally opened malicious workspace.

Incident Response Considerations

If suspicious notebook content or unexpected process activity is identified:

1. Disconnect the affected host from sensitive networks while preserving evidence.
2. Record the SiYuan version, installation path, operating-system account, and workspace locations.
3. Preserve relevant notebook files, application logs, endpoint telemetry, and process trees.
4. Identify any shells, scripting engines, download utilities, or other child processes launched by SiYuan.
5. Review recently modified files, persistence mechanisms, and outbound connections.
6. Rotate credentials accessible to the affected operating-system account.
7. Reinstall or upgrade SiYuan only after collecting the evidence needed for investigation.
8. Restore notebooks from trusted backups after validating their contents.

If the application ran with access to sensitive files or credentials, assume those resources may have been exposed until the investigation demonstrates otherwise.

References

The primary reference is the NVD record for CVE-2026-93922. It provides the affected product and version range, the 8.8 High severity rating, the stored-XSS description, and links to the vendor’s security advisory and source-code references:

• NVD: CVE-2026-93922
• SiYuan GitHub Security Advisory
• SiYuan source: mount.ts at version 3.8.4
• SiYuan source: file.go at version 3.8.4

Additional context is available from the SiYuan project repository and the VulnCheck advisory. Check these references for a confirmed remediation release because the available data does not identify a fixed version:

• SiYuan GitHub repository
• VulnCheck advisory: SiYuan through 3.8.4

CVE-2026-93922 should be treated as a high-priority application and endpoint risk for organizations using affected SiYuan versions. No confirmed in-the-wild exploitation or public proof of concept is established, but the reported Electron and Node.js execution context makes timely containment, monitoring, and verified patching important.

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