{"id":"GHSA-gpfj-4j6g-c4w9","summary":"Clipboard-based DOM-XSS","details":"### Impact\n\nA self Cross-Site Scripting vulnerability exists in the @github/paste-markdown library. If the clipboard data contains the string `\u003ctable\u003e`, a **div** is dynamically created, and the clipboard content is copied into its **innerHTML** property without any sanitization, resulting in improper execution of JavaScript in the browser of the victim (the user who pasted the code). Users directed to copy text from a malicious website and paste it into pages that utilize this library are affected.\n\nThe following @github/paste-markdown code snippet is triggered when the user pastes something and the browser's clipboard data contains an entry whose content-type is **text/HTML**.\n\n```typescript\nfunction generateText(transfer: DataTransfer): string | undefined {\n  if (Array.from(transfer.types).indexOf('text/html') === -1) return\n\n  let html = transfer.getData('text/html')\n  if (!/\u003ctable/i.test(html)) return\n\n  html = html.replace(/\u003cmeta.*?\u003e/, '')\n\n  const el = document.createElement('div')\n  el.innerHTML = html\n  const tables = el.querySelectorAll('table')\n\n  for (const table of tables) {\n    if (table.closest('[data-paste-markdown-skip]')) {\n      table.replaceWith(new Text(table.textContent || ''))\n    }\n    const formattedTable = tableMarkdown(table)\n    table.replaceWith(new Text(formattedTable))\n  }\n\n  return el.innerHTML\n}\n```\n\n### Patches\nA security patch was released in [version 0.3.4](https://github.com/github/paste-markdown/releases/tag/v0.3.4).\n\n### Workarounds\nA Content Security Policy that prevents `unsafe-inline` helps reduce the likelihood of this vulnerability being exploited in modern browsers.\n\n\u003c!--\n### References\n_Are there any links users can visit to find out more?_\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [example link to repo](http://example.com)\n* Email us at [example email address](mailto:example@example.com)\n*\n--\u003e\n","aliases":["CVE-2021-37700"],"modified":"2026-07-08T06:28:23.280733876Z","published":"2021-08-12T20:42:17Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2021-08-12T20:41:45Z","nvd_published_at":"2021-08-12T21:15:00Z","cwe_ids":["CWE-79"],"severity":"MODERATE"},"references":[{"type":"WEB","url":"https://github.com/github/paste-markdown/security/advisories/GHSA-gpfj-4j6g-c4w9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-37700"},{"type":"WEB","url":"https://github.com/github/paste-markdown/commit/32b7ea3f29ae8f256f9d19768387be42678ddf30"},{"type":"PACKAGE","url":"https://github.com/github/paste-markdown"},{"type":"WEB","url":"https://github.com/github/paste-markdown/releases/tag/v0.3.4"},{"type":"WEB","url":"https://www.npmjs.com/package/@github/paste-markdown"}],"affected":[{"package":{"name":"@github/paste-markdown","ecosystem":"npm","purl":"pkg:npm/%40github/paste-markdown"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.3.4"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/08/GHSA-gpfj-4j6g-c4w9/GHSA-gpfj-4j6g-c4w9.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"}]}