{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.10.1"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "league/commonmark"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.3.0"
            },
            {
              "fixed": "2.10.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-78",
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-30T15:36:33Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "\ufeff## Summary\n\nThe `DisallowedRawHtml` extension does not escape a disallowed tag when the tag name is the last thing in the raw HTML. A Markdown line containing just `\u003cscript` is emitted unchanged, and the next block can supply its attributes. With the shipped GFM defaults this allows stored XSS by anyone who can post Markdown.\n\n## Details\n\n`DisallowedRawHtmlRenderer` escapes tags with this regex:\n\n```\n/\u003c(\\/?(?:title|textarea|style|xmp|iframe|noembed|noframes|script|plaintext)[\\s\\/\u003e])/i\n```\n\nThe trailing character class requires one character after the tag name. The block parser does not: `RegexHelper::PARTIAL_HTMLBLOCKOPEN` accepts end of line after a tag name, so `\u003cscript` alone opens an HTML block. Because a rendered `HtmlBlock` has no trailing newline, the regex has nothing to match and the `\u003c` passes through.\n\nIn the browser the newline is still present, so the tag name terminates there and whatever follows becomes attributes.\n\nThis is the same filter that GHSA-4v6x-c7xx-hw9f fixed in 2.8.1. That fix widened the character class but still requires one character, so this case was not covered.\n\n## Reproduction\n\nRender this with `GithubFlavoredMarkdownConverter` and default settings:\n\n```\n\u003cdiv\u003e\n\u003cscript\n\n\u003cspan src=\"/evil.js\"\u003e\n```\n\nOutput:\n\n```html\n\u003cdiv\u003e\n\u003cscript\n\u003cspan src=\"/evil.js\"\u003e\n```\n\nA browser parses that as `\u003cscript src=\"/evil.js\"\u003e` with a junk `\u003cspan` attribute, and the script runs. `\u003ciframe` with `\u003cspan onload=\"...\"\u003e` works the same way and does not need a later `\u003c/script\u003e` in the page.\n\nControl: `\u003cscript src=\"/evil.js\"\u003e\u003c/script\u003e` is correctly escaped to `\u0026lt;script src=\"/evil.js\"\u003e\u0026lt;/script\u003e`.\n\n## Affected versions\n\n1.3.0 (when the extension was added) through the current release. The `\u003c/style` and mid-line forms are only affected as continuation lines inside an already-open HTML block.\n\n## Preconditions\n\n- `html_input` is `allow` (the default)\n- The `DisallowedRawHtml` extension is active, which the GFM extension enables automatically\n- Untrusted users can post Markdown\n\nSetting `html_input` to `escape` or `strip` fully mitigates this.\n\n## Suggested fix\n\nAllow end of string after the tag name:\n\n```php\n$regex = \\sprintf(\u0027/\u003c(\\/?(?:%s))([\\s\\/\u003e]|$)/i\u0027, \\implode(\u0027|\u0027, \\array_map(\u0027preg_quote\u0027, $tags)));\n\nreturn \\preg_replace($regex, \u0027\u0026lt;$1$2\u0027, $rendered);\n```\n\nThis escapes every bypass shape above and leaves `\u003cdiv\u003e`, `\u003cscripts\u003e` and `\u003cspan class=\"a\"\u003e` untouched. The existing unit test only covers tag names followed by another character, so a case for a bare tag name should be added.",
  "id": "GHSA-97jj-33gv-5xf9",
  "modified": "2026-09-30T15:36:33Z",
  "published": "2026-09-30T15:36:33Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/thephpleague/commonmark/security/advisories/GHSA-97jj-33gv-5xf9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/thephpleague/commonmark/commit/411afcc2a7402756d96c89af8882c724d12d47ca"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/thephpleague/commonmark"
    },
    {
      "type": "WEB",
      "url": "https://github.com/thephpleague/commonmark/releases/tag/2.10.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "league/commonmark: DisallowedRawHtml bypassed when a disallowed tag name ends the raw-HTML literal"
}