Discourse: Stored XSS via unescaped actor name in post actions

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-59830",
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "dateUpdated": "2026-09-21T21:17:38.733Z",
    "dateReserved": "2026-07-07T15:00:50.979Z",
    "datePublished": "2026-09-21T21:17:38.733Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M",
        "dateUpdated": "2026-09-21T21:17:38.733Z"
      },
      "title": "Discourse: Stored XSS via unescaped actor name in post actions",
      "descriptions": [
        {
          "lang": "en",
          "value": "Discourse is an open-source discussion platform. Prior to 2026.7.0, the post action component failed to escape user-controlled display names before interpolating them into an HTML string passed to trustHTML. A user who could choose a crafted display name could persist markup in post action descriptions. Viewing the affected user activity streams could execute attacker-controlled script in another user's browser. This issue is fixed in version 2026.7.0."
        }
      ],
      "affected": [
        {
          "vendor": "discourse",
          "product": "discourse",
          "versions": [
            {
              "version": "< 2026.7.0",
              "status": "affected"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')",
              "cweId": "CWE-79",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://github.com/discourse/discourse/security/advisories/GHSA-x6mf-p7cg-69rw",
          "name": "https://github.com/discourse/discourse/security/advisories/GHSA-x6mf-p7cg-69rw",
          "tags": [
            "x_refsource_CONFIRM"
          ]
        },
        {
          "url": "https://github.com/discourse/discourse/commit/dd786594ddd088657a7e6f9fefba5bd889965fe4",
          "name": "https://github.com/discourse/discourse/commit/dd786594ddd088657a7e6f9fefba5bd889965fe4",
          "tags": [
            "x_refsource_MISC"
          ]
        },
        {
          "url": "https://github.com/discourse/discourse/releases/tag/v2026.7.0",
          "name": "https://github.com/discourse/discourse/releases/tag/v2026.7.0",
          "tags": [
            "x_refsource_MISC"
          ]
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "version": "3.1",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
            "attackVector": "NETWORK",
            "attackComplexity": "LOW",
            "privilegesRequired": "LOW",
            "userInteraction": "REQUIRED",
            "scope": "CHANGED",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "availabilityImpact": "NONE",
            "baseScore": 5.4,
            "baseSeverity": "MEDIUM"
          }
        }
      ]
    }
  }
}