Vulnerability from bitnami_vulndb
Published
2026-10-01 09:29
Modified
2026-10-01 09:55
Summary
Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist
Details

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the Discourse post sanitizer allowed a stored cross-origin iframe to bypass the allowed_iframes prefix policy when the iframe src contained encoded userinfo. The sanitizer validated a decoded form differently from the stored iframe src, allowing the browser to interpret an attacker-controlled host while the allowlist check accepted the encoded URL as an allowed prefix. An authenticated user with posting privileges could persist the iframe in a post and cause attacker-controlled cross-origin content to be rendered. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Bitnami",
        "name": "discourse",
        "purl": "pkg:bitnami/discourse"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2026.8.0"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
          "type": "CVSS_V3"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-91134"
  ],
  "database_specific": {
    "cpes": [
      "cpe:2.3:a:discourse:discourse:*:*:*:*:stable:*:*:*",
      "cpe:2.3:a:discourse:discourse:*:*:*:*:beta:*:*:*"
    ],
    "severity": "Medium"
  },
  "details": "Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the Discourse post sanitizer allowed a stored cross-origin iframe to bypass the allowed_iframes prefix policy when the iframe src contained encoded userinfo. The sanitizer validated a decoded form differently from the stored iframe src, allowing the browser to interpret an attacker-controlled host while the allowlist check accepted the encoded URL as an allowed prefix. An authenticated user with posting privileges could persist the iframe in a post and cause attacker-controlled cross-origin content to be rendered. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.",
  "id": "BIT-discourse-2026-91134",
  "modified": "2026-10-01T09:55:18.588Z",
  "published": "2026-10-01T09:29:34.915Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/discourse/discourse/commit/0a8015e6c7a5079981843721494d30c9a91f5415"
    },
    {
      "type": "WEB",
      "url": "https://github.com/discourse/discourse/commit/1304b0c04f87534053b0d574ae5a9b9ba13dd590"
    },
    {
      "type": "WEB",
      "url": "https://github.com/discourse/discourse/commit/bac7dd1201911851462483271b4567246fa1309d"
    },
    {
      "type": "WEB",
      "url": "https://github.com/discourse/discourse/commit/fed3a58c48412ce7207b72a4629ddbc44482cd64"
    },
    {
      "type": "WEB",
      "url": "https://github.com/discourse/discourse/pull/42882"
    },
    {
      "type": "WEB",
      "url": "https://github.com/discourse/discourse/security/advisories/GHSA-54vw-chv3-wjpv"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-91134"
    }
  ],
  "schema_version": "1.6.2",
  "summary": "Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist"
}



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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.

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