star7th showdoc up to 3.9.1 API Page Save Endpoint editormd.js cross site scripting

Summaryinfo

A vulnerability classified as problematic has been found in star7th showdoc up to 3.9.1. This issue affects some unknown processing of the file web_src/public/editor.md/editormd.js of the component API Page Save Endpoint. The manipulation leads to cross site scripting. This vulnerability is referenced as CVE-2026-86644. Remote exploitation of the attack is possible. Furthermore, an exploit is available. It is recommended to upgrade the affected component. The vendor confirms: "The fix [...] sets Mermaid `securityLevel` to `strict`, disables `htmlLabels`, and sanitizes rendered SVG with DOMPurify."

Detailsinfo

A vulnerability, which was classified as problematic, has been found in star7th showdoc up to 3.9.1. This issue affects some unknown processing of the file web_src/public/editor.md/editormd.js of the component API Page Save Endpoint. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity.

It is possible to read the advisory at gist.github.com. The identification of this vulnerability is CVE-2026-86644. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. Technical details as well as a public exploit are known. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

The exploit is available at gist.github.com. It is declared as proof-of-concept. The vendor confirms: "The fix [...] sets Mermaid `securityLevel` to `strict`, disables `htmlLabels`, and sanitizes rendered SVG with DOMPurify."

Upgrading to version 3.9.2 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch a8ea1520850b4242f395247f72e87e597506cef0 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• star7th

Name

• showdoc

Version

• 3.9.0
• 3.9.1

License

• open-source

Website

• Product: https://github.com/star7th/showdoc/

CPE 2.3info

• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒

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Submitinfo

Accepted

• Submit #906282: star7th ShowDoc 3.7.1 - 3.9.1 Cross Site Scripting (by LIU Tingwei)

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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