Cross Site Scripting Vulnerability in star7th ShowDoc API Page Save Endpoint
CVE-2026-86644

5.1MEDIUM

Key Information:

Vendor

Star7th

Status
Showdoc
Vendor
CVE Published:
8 September 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-86644?

A vulnerability was identified in star7th ShowDoc through version 3.9.1, specifically within the API Page Save Endpoint in the file web_src/public/editor.md/editormd.js. This flaw can be exploited remotely via crafted inputs, leading to potential cross site scripting attacks. To mitigate these risks, users are strongly advised to upgrade to version 3.9.2, which introduces security enhancements including setting Mermaid securityLevel to strict, disabling htmlLabels, and sanitizing SVG output with DOMPurify.

Affected Version(s)

showdoc 3.9.0

showdoc 3.9.1

showdoc 3.9.2

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-86644 - Proof of Concept

References

https://vuldb.com/vuln/399755
vdb-entry
https://vuldb.com/vuln/399755/cti
signaturepermissions-required
https://vuldb.com/cve/CVE-2026-86644
third-party-advisory

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

LIU Tingwei (VulDB User)
VulDB CNA Team
.