# CVE-2026-81899: Concrete CMS 9.0 to 9.5.2 is vulnerable to Stored XSS via group folder name on the Members > Groups dashboard

> Authenticated users can inject scripts via group folder names, leading to XSS and potential administrator session hijacking in Concrete CMS.

- **Severity:** High 7.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 15 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** GHSA-3cxg-c254-578m

## What is CVE-2026-81899?

CVE-2026-81899 is a high-severity cross-site scripting vulnerability in Concrete CMS, published on 15 Sep 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

Concrete CMS 9.0.0 to 9.5.2 stored group folder names without sanitization and printed them unescaped on the Members > Groups dashboard page, resulting in stored cross-site scripting. The add and edit group-folder handlers stored the submitted folder name without neutralizing HTML, and the group search grid returned it without output encoding, so the Groups dashboard rendered the name as live markup. An authenticated user holding the Add Group Folder permission could store a script payload as a folder name that executed in the session of any administrator who viewed the Groups dashboard, enabling session and token theft and any action available in the administrator's context. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Lý Chấn Hưng (hunglyvn) for reporting.

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

## Which versions are affected by CVE-2026-81899?


## How do I fix CVE-2026-81899?

No fix has been published for CVE-2026-81899 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81899 being exploited?

There is no known exploitation of CVE-2026-81899 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81899 and fix it if it is affected.

What it is: CVE-2026-81899 is a high-severity cross-site scripting vulnerability in Concrete CMS, published on 15 Sep 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-81899 in the wild and no public exploit code.

Affected product: Concrete CMS. 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-2026-81899/ (Markdown: https://insights.sbomify.com/CVE-2026-81899/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81899
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81899
- OSV: https://osv.dev/vulnerability/CVE-2026-81899

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-81899/
Summaries are generated and may contain mistakes; the official description above is the record.