Isso: Stored XSS via comment website field

{
  "id": "5cf0aa2c825c591c699d550eb0b132193cfa64881969c6bed2f393166277d17e",
  "url": "https://osv.dev/vulnerability/CVE-2026-27469",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Isso: Stored XSS via comment website field",
    "summary": "Isso is a lightweight commenting server written in Python and JavaScript. In commits before 0afbfe0691ee237963e8fb0b2ee01c9e55ca2144, there is a stored Cross-Site Scripting (XSS) vulnerability affecting the website and author comment fields. The website field was HTML-escaped using quote=False, which left single and double quotes unescaped. Since the frontend inserts the website value directly into a single-quoted href attribute via string concatenation, a single quote in the URL breaks out of the attribute context, allowing injection of arbitrary event handlers (e.g. onmouseover, onclick). The same escaping is missing entirely from the user-facing comment edit endpoint (PUT /id/) and the moderation edit endpoint (POST /id//edit/). This issue has been patched in commit 0afbfe0691ee237963e8fb0b2ee01c9e55ca2144. To workaround, nabling comment moderation (moderation = enabled = true in isso.cfg) prevents unauthenticated users from publishing comments, raising the bar for exploitation, but it does not fully mitigate the issue since a moderator activating a malicious comment would still expose visitors.",
    "evidence": "osv:CVE-2026-27469",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-27469",
      "aliases": [
        "CVE-2026-27469",
        "GHSA-9fww-8cpr-q66r",
        "PYSEC-2026-2527"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/isso-comments/isso",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0afbfe0691ee237963e8fb0b2ee01c9e55ca2144"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0afbfe0691ee237963e8fb0b2ee01c9e55ca2144"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0afbfe0691ee237963e8fb0b2ee01c9e55ca2144"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "0.13.1.dev0",
            "0.13.0",
            "0.12.6-pre",
            "0.12.6",
            "0.12.5",
            "0.12.4",
            "0.12.2",
            "0.12.1",
            "0.12.0",
            "0.11.1",
            "0.11.0",
            "upstream/0.10.6+git20170928",
            "0.10.6",
            "0.10.5",
            "upstream/0.10.4",
            "0.10.4",
            "0.10.3",
            "0.10.2",
            "0.10.1",
            "0.10",
            "0.9",
            "0.8",
            "0.7",
            "0.5",
            "0.4",
            "0.3",
            "0.2.1",
            "0.2"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-27469.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:23.825311613Z",
      "provider": "osv",
      "references": [
        "https://docs.python.org/3/library/html.html#html.escape",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27469.json",
        "https://github.com/isso-comments/isso/security/advisories/GHSA-9fww-8cpr-q66r",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-27469",
        "https://github.com/isso-comments/isso/commit/0afbfe0691ee237963e8fb0b2ee01c9e55ca2144"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-116",
          "CWE-79"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27469.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-27469",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 490068,
  "published_at": "2026-02-21T07:24:38.971+00:00"
}