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LOW severity

Concrete CMS Stored XSS in the Custom Class page editingGHSA-r7q4-cw9r-vhp4

LOWFix: concretecms/concretecms#11988

GHSA-r7q4-cw9r-vhp4 is a low-severity (CVSS 3.1) Cross-site Scripting (XSS) vulnerability in concrete5/concrete5. A fix is available for concrete5/concrete5 — see the affected versions and patch details below.

Also known asCVE-2024-3179
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-r7q4-cw9r-vhp4.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs30th percentile — riskier than 30% of all scored CVEsHighest risk
0.00%0.29%0.57%0.86%0.1%0.4%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
🐘concrete5/concrete5🐘concrete5/concrete5

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Concrete CMS version 9 before 9.2.8 and previous versions before 8.5.16 are vulnerable to Stored XSS in the Custom Class page editing. Prior to the fix, a rogue administrator could insert malicious code in the custom class field due to insufficient validation of administrator provided data. The Concrete CMS security team gave this vulnerability a CVSS v3.1 score of 3.1 with a vector of AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:L https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator . Thanks Alexey Solovyev for reporting. 

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistconcrete5/concrete5≥ 9.0.0RC1&&< 9.2.89.2.8composer require concrete5/concrete5:^9.2.8
🐘Packagistconcrete5/concrete5all versions8.5.16composer require concrete5/concrete5:^8.5.16

Affected Products

1 product · 2 configurations
Application
concrete cmsconcretecms
≥ 9.0.0 && < 9.2.8
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for concrete5/concrete5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update concrete5/concrete5 to 9.2.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-r7q4-cw9r-vhp4 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

Concrete CMS version 9 before 9.2.8 and previous versions before 8.5.16 are vulnerable to Stored XSS in the Custom Class page editing. Prior to the fix, a rogue administrator could insert malicious code in the custom class field due to insufficient validation of administrator provided data. The Concrete CMS security team gave this vulnerability a CVSS v3.1 score of 3.1 with a vector of AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:L https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator . Thanks Alexey Solovyev for reporting. 
O3 Security · Impact-Aware SCA

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Concrete CMS Stored XSS in the Custom Class page…