GHSA-gpfj-4j6g-c4w9

Dashboard / Vulnerabilities / GHSA-gpfj-4j6g-c4w9

GHSA-gpfj-4j6g-c4w9

Summary: Clipboard-based DOM-XSS

Details: ### Impact A self Cross-Site Scripting vulnerability exists in the @github/paste-markdown library. If the clipboard data contains the string `<table>`, 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. The 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**. ```typescript function generateText(transfer: DataTransfer): string | undefined { if (Array.from(transfer.types).indexOf('text/html') === -1) return let html = transfer.getData('text/html') if (!/<table/i.test(html)) return html = html.replace(/<meta.*?>/, '') const el = document.createElement('div') el.innerHTML = html const tables = el.querySelectorAll('table') for (const table of tables) { if (table.closest('[data-paste-markdown-skip]')) { table.replaceWith(new Text(table.textContent || '')) } const formattedTable = tableMarkdown(table) table.replaceWith(new Text(formattedTable)) } return el.innerHTML } ``` ### Patches A security patch was released in [version 0.3.4](https://github.com/github/paste-markdown/releases/tag/v0.3.4). ### Workarounds A Content Security Policy that prevents `unsafe-inline` helps reduce the likelihood of this vulnerability being exploited in modern browsers. <!-- ### References _Are there any links users can visit to find out more?_ ### For more information If you have any questions or comments about this advisory: * Open an issue in [example link to repo](http://example.com) * Email us at [example email address](mailto:[email protected]) * -->

References: https://github.com/github/paste-markdown/security/advisories/GHSA-gpfj-4j6g-c4w9, https://nvd.nist.gov/vuln/detail/CVE-2021-37700, https://github.com/github/paste-markdown/commit/32b7ea3f29ae8f256f9d19768387be42678ddf30, https://github.com/github/paste-markdown, https://github.com/github/paste-markdown/releases/tag/v0.3.4, https://www.npmjs.com/package/@github/paste-markdown