# CVE-2026-81753: Flowintel Stored XSS in Case Notes via Malicious Mermaid Diagram Content

> Attackers can execute JavaScript in other users' browsers by storing malicious Mermaid diagrams in case notes, potentially leading to account takeover.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 27 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** GHSA-4xww-rqhr-67w2

## What is CVE-2026-81753?

CVE-2026-81753 is a medium-severity cross-site scripting vulnerability in flowintel, published on 27 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official 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

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-81753?


## How do I fix CVE-2026-81753?

No fix has been published for CVE-2026-81753 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81753 being exploited?

There is no known exploitation of CVE-2026-81753 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81753 and fix it if it is affected.

What it is: CVE-2026-81753 is a medium-severity cross-site scripting vulnerability in flowintel, published on 27 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-81753 in the wild and no public exploit code.

Affected product: flowintel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-81753/ (Markdown: https://insights.sbomify.com/CVE-2026-81753/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81753
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81753
- OSV: https://osv.dev/vulnerability/CVE-2026-81753

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81753/
Summaries are generated and may contain mistakes; the official description above is the record.