GHSA-628F-V4F6-P37R

Vulnerability from github – Published: 2026-10-09 20:53 – Updated: 2026-10-09 20:53
VLAI
Summary
Contao: Cross-site scripting in the comments bundle
Details

An unauthenticated front end visitor can post a comment containing a XSS injection. The victim is any back end user who opens the Comments module, and moderation makes exposure certain rather than preventing it. No Content-Security-Policy header is sent on the Contao back end, so nothing mitigates the inline handler.

Impact

Anyone on the internet can inject script that executes in the Contao back end origin, under the session of whichever user opens the Comments module, with no click and no hover. From there the payload acts as that user through the back end: reading any module they can reach, creating a new administrator, or editing a template, which on Contao is a documented path from back end write access to code execution. Moderation does not help and in fact guarantees exposure, since unpublished comments are still inserted and a moderator has to open the list to act on them.

Severity
9.3 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "contao/comments-bundle"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "5.3.50"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "contao/comments-bundle"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.4.0-RC1"
            },
            {
              "fixed": "5.7.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-107845"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-116",
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-09T20:53:50Z",
    "nvd_published_at": null,
    "severity": "CRITICAL"
  },
  "details": "An unauthenticated front end visitor can post a comment containing a XSS injection. The victim is any back end user who opens the Comments module, and moderation makes exposure certain rather than preventing it. No `Content-Security-Policy` header is sent on the Contao back end, so nothing mitigates the inline handler.\n\n### Impact\n\nAnyone on the internet can inject script that executes in the Contao back end origin, under the session of whichever user opens the Comments module, with no click and no hover. From there the payload acts as that user through the back end: reading any module they can reach, creating a new administrator, or editing a template, which on Contao is a documented path from back end write access to code execution. Moderation does not help and in fact guarantees exposure, since unpublished comments are still inserted and a moderator has to open the list to act on them.",
  "id": "GHSA-628f-v4f6-p37r",
  "modified": "2026-10-09T20:53:51Z",
  "published": "2026-10-09T20:53:50Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/contao/contao/security/advisories/GHSA-628f-v4f6-p37r"
    },
    {
      "type": "WEB",
      "url": "https://github.com/contao/contao/commit/22505d5f79bc1a7f52e2cba5fddf6007e1f0408a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/contao/contao"
    },
    {
      "type": "WEB",
      "url": "https://github.com/contao/contao/releases/tag/5.3.50"
    },
    {
      "type": "WEB",
      "url": "https://github.com/contao/contao/releases/tag/5.7.12"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Contao: Cross-site scripting in the comments bundle"
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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