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CVE-2026-81753

Flowintel Stored XSS in Case Notes via Malicious Mermaid Diagram Content

5.1 Medium

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

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
Passive

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
None

Exploit likelihood

0.55%Up 0.2 points since Aug 28, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.1

Flowintel Stored XSS in Case Notes via Malicious Mermaid Diagram Content

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

Record
CVE-2026-81753
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
Weakness
CWE-79
Updated
2026-11-02
EUVDEUVD-2026-67009 5.1

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

Record
EUVD-2026-67009
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-4xww-rqhr-67w2 5.1

Affected versions of Flowintel render Mermaid blocks contained in stored case notes without...

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

Record
GHSA-4xww-rqhr-67w2
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness
CWE-79
Updated
2026-11-02
NVD 5.1

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

Record
CVE-2026-81753
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness
CWE-79
Updated
2026-11-02
OSV 5.1

Flowintel Stored XSS in Case Notes via Malicious Mermaid Diagram Content

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

Record
CVE-2026-81753
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
Weakness
CWE-79
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
aliases, publishedEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-81753 is a medium vulnerability (CVSS 5.1) in Flowintel, published August 27, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.55%, the 46th percentile. No source names a fixed version.

References

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