GHSA-GPFJ-4J6G-C4W9
Vulnerability from github – Published: 2021-08-12 20:42 – Updated: 2021-08-30 23:16
VLAI?
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.
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.
Workarounds
A Content Security Policy that prevents unsafe-inline helps reduce the likelihood of this vulnerability being exploited in modern browsers.
Severity ?
6.5 (Medium)
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "@github/paste-markdown"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.3.4"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2021-37700"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2021-08-12T20:41:45Z",
"nvd_published_at": "2021-08-12T21:15:00Z",
"severity": "MODERATE"
},
"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\u0027s 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(\u0027text/html\u0027) === -1) return\n\n let html = transfer.getData(\u0027text/html\u0027)\n if (!/\u003ctable/i.test(html)) return\n\n html = html.replace(/\u003cmeta.*?\u003e/, \u0027\u0027)\n\n const el = document.createElement(\u0027div\u0027)\n el.innerHTML = html\n const tables = el.querySelectorAll(\u0027table\u0027)\n\n for (const table of tables) {\n if (table.closest(\u0027[data-paste-markdown-skip]\u0027)) {\n table.replaceWith(new Text(table.textContent || \u0027\u0027))\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",
"id": "GHSA-gpfj-4j6g-c4w9",
"modified": "2021-08-30T23:16:08Z",
"published": "2021-08-12T20:42:17Z",
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "Clipboard-based DOM-XSS"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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