CVE-2026-81753
Received Received - Intake

Stored XSS in Flowintel via Mermaid Block Rendering

Publication date: 2026-08-27

Last updated on: 2026-08-27

Assigner: CIRCL

Description
Affected versions of Flowintel render Mermaid blocks contained in stored case notes without sufficiently neutralizing attacker-controlled markup. Because Mermaid note content is persisted and later rendered for other users, an attacker with permission to create or edit a note could store a crafted Mermaid payload that results in JavaScript execution when another user views the affected case note. The patch adds explicit Mermaid detection and HTML escaping around the token content before the generated Mermaid wrapper is returned. It also moves the wrapping logic earlier in page initialization so Markdown instances are protected consistently. Version impacted >= 3.3.0

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Meta Information

Published
2026-08-27
Last Modified
2026-08-27
Generated
2026-08-27
AI Q&A
2026-08-27
EPSS Evaluated
N/A
NVD
CVE-2026-81753
EUVD
EUVD-2026-67009

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
flowintel flowintel From 3.3.0 (inc)

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Exploitability

CWE
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KEV
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CWE ID Description
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.

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Executive Summary

This is a stored Cross-Site Scripting (XSS) vulnerability in Flowintel versions 3.3.0 and above. Attackers with note creation permissions can inject malicious JavaScript code into Mermaid diagram blocks within stored case notes. When other users view these notes, the JavaScript executes in their browser due to insufficient sanitization of Mermaid content.

Detection Guidance

Check for Flowintel versions >= 3.3.0. Inspect case notes containing Mermaid blocks for unexpected JavaScript execution when rendered. Review Markdown rendering logic for improper HTML escaping in Mermaid content.

Impact Analysis

An attacker could steal session cookies, perform actions on your behalf, or redirect you to malicious sites. If you view affected case notes, your browser may execute attacker-controlled scripts, compromising your account or data.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality principles or HIPAA's safeguards for protected health information. Organizations may face compliance violations if user data is compromised through this exploit.

Mitigation Strategies

Update Flowintel to the patched version. Ensure Mermaid content in case notes is properly sanitized by adding explicit detection and HTML escaping before rendering. Move wrapping logic earlier in page initialization to protect all Markdown instances.

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