GHSA-533c-2vh9-4r86

Suggest an improvement
Source
https://github.com/advisories/GHSA-533c-2vh9-4r86
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-533c-2vh9-4r86/GHSA-533c-2vh9-4r86.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-533c-2vh9-4r86
Aliases
Published
2026-07-13T17:18:12Z
Modified
2026-07-13T17:41:46Z
Severity
  • 4.8 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N CVSS Calculator
Summary
Decidim: HTML content blocks allow stored script execution
Details

Description

A privileged admin user who can edit an affected landing page can store arbitrary HTML/JavaScript in an HTML block, and the public page renders it with html_safe and no output escaping.

Technical description

This issue lets any admin who can edit an affected landing page store arbitrary HTML and JavaScript in an HTML block. The block is then rendered back through Decidim::ContentBlocks::HtmlCell#html_content without a sanitization boundary, so the script executes later in visitor's browsers.

decidim-html-xss-01 decidim-html-xss-02

Impact

  • A user with landing-page editing rights for an affected scope can persist JavaScript that executes in visitor's browsers on that page.
  • Because exploitation already requires privileged administrative access, the practical risk is lower than a participant-controlled or unauthenticated stored XSS. It still creates a browser-execution primitive in a trusted admin-editable surface.

Patches

See https://github.com/decidim/decidim/pull/16451

Workarounds

Do not give admin permissions to non-trustful users.

Reference

Stored XSS

Credits

This issue was discovered in a security audit organized by the Decidim Association and made by Radically Open Security against Decidim financed by NGI.

Database specific 
{
    "cwe_ids":  [
        "CWE-94"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-07-13T17:18:12Z",
    "nvd_published_at":  null,
    "severity":  "MODERATE"
}
References

Affected packages

RubyGems / decidim-core

Package

Name
decidim-core
Purl
pkg:gem/decidim-core

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
0.30.9

Affected versions

0.*
0.0.1.alpha1
0.0.1.alpha2
0.0.1.alpha3
0.0.1.alpha4
0.0.1.alpha5
0.0.1.alpha6
0.0.1.alpha7
0.0.1.alpha8
0.0.1.alpha9
0.0.1
0.0.2
0.0.3
0.0.5
0.0.6
0.0.7
0.0.8.1
0.1.0
0.2.0
0.3.0
0.3.1
0.3.2
0.4.0
0.4.1
0.4.2
0.4.3
0.4.4
0.5.0
0.5.1
0.6.0
0.6.1
0.6.2
0.6.3
0.6.4
0.6.5
0.6.6
0.6.7
0.6.8
0.7.0
0.7.1
0.7.2
0.7.3
0.7.4
0.8.0
0.8.1
0.8.2
0.8.3
0.8.4
0.9.0
0.9.1
0.9.2
0.9.3
0.10.0
0.10.1
0.11.0.pre1
0.11.1
0.11.2
0.12.0.pre
0.12.0
0.12.1
0.12.2
0.13.0.pre1
0.13.0
0.13.1
0.14.1
0.14.2
0.14.3
0.14.4
0.15.0
0.15.1
0.15.2
0.16.0
0.16.1
0.17.0
0.17.1
0.17.2
0.18.0
0.18.1
0.19.0
0.19.1
0.20.0
0.20.1
0.21.0
0.22.0
0.23.0
0.23.1.rc1
0.23.1
0.23.2
0.23.3
0.23.4
0.23.5
0.23.6
0.24.0.rc1
0.24.0.rc2
0.24.0
0.24.1
0.24.2
0.24.3
0.25.0.rc1
0.25.0.rc2
0.25.0.rc3
0.25.0.rc4
0.25.0
0.25.1
0.25.2
0.26.0.rc1
0.26.0.rc2
0.26.0
0.26.1
0.26.2
0.26.3
0.26.4
0.26.5
0.26.7
0.26.8
0.26.9
0.26.10
0.27.0.rc1
0.27.0.rc2
0.27.0
0.27.1
0.27.2
0.27.3
0.27.4
0.27.5
0.27.6
0.27.7
0.27.8
0.27.9
0.27.10
0.28.0.rc4
0.28.0.rc5
0.28.0
0.28.1
0.28.2
0.28.3
0.28.4
0.28.5
0.28.6
0.29.0.rc1
0.29.0.rc2
0.29.0.rc3
0.29.0.rc4
0.29.0
0.29.1
0.29.2
0.29.3
0.29.4
0.29.5
0.29.6
0.29.7
0.30.0.rc1
0.30.0.rc2
0.30.0.rc3
0.30.0
0.30.1
0.30.2
0.30.3
0.30.4
0.30.5
0.30.6
0.30.7
0.30.8

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-533c-2vh9-4r86/GHSA-533c-2vh9-4r86.json"

RubyGems / decidim-core

Package

Name
decidim-core
Purl
pkg:gem/decidim-core

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0.31.0.rc1
Fixed
0.31.5

Affected versions

0.*
0.31.0.rc1
0.31.0.rc2
0.31.0
0.31.1
0.31.2
0.31.3
0.31.4

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-533c-2vh9-4r86/GHSA-533c-2vh9-4r86.json"

RubyGems / decidim-core

Package

Name
decidim-core
Purl
pkg:gem/decidim-core

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0.32.0.rc1
Fixed
0.32.0

Affected versions

0.*
0.32.0.rc1
0.32.0.rc2
0.32.0.rc3

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-533c-2vh9-4r86/GHSA-533c-2vh9-4r86.json"