{"id":"GHSA-52c5-vh7f-26fx","summary":"Cross-Site Scripting (XSS) vulnerability through unescaped HTML attribute values","details":"### Impact\n\nThe prosemirror_to_html gem is vulnerable to Cross-Site Scripting (XSS) attacks through malicious HTML attribute values. While tag content is properly escaped, attribute values are not, allowing attackers to inject arbitrary JavaScript code.\n\n**Who is impacted:**\n- Any application using prosemirror_to_html to convert ProseMirror documents to HTML\n- Applications that process user-generated ProseMirror content are at highest risk\n- End users viewing the rendered HTML output could have malicious JavaScript executed in their browsers\n\n**Attack vectors include:**\n- `href` attributes with `javascript:` protocol: `\u003ca href=\"javascript:alert(document.cookie)\"\u003e`\n- Event handlers: `\u003cdiv onclick=\"maliciousCode()\"\u003e`\n- `onerror` attributes on images: `\u003cimg src=x onerror=\"alert('XSS')\"\u003e`\n- Other HTML attributes that can execute JavaScript\n\n### Patches\n\nA fix is currently in development. Users should upgrade to version **0.2.1** or later once released.\n\nThe patch escapes all HTML attribute values using `CGI.escapeHTML` to prevent injection attacks.\n\n### Workarounds\n\nUntil a patched version is available, users can implement one or more of these mitigations:\n\n1. **Sanitize output**: Pass the HTML output through a sanitization library like [Sanitize](https://github.com/rgrove/sanitize) or [Loofah](https://github.com/flavorjones/loofah):\n```ruby\n   html = ProsemirrorToHtml.render(document)\n   safe_html = Sanitize.fragment(html, Sanitize::Config::RELAXED)\n```\n\n2. **Implement Content Security Policy (CSP)**: Add strict CSP headers to prevent inline JavaScript execution:\n```\n   Content-Security-Policy: default-src 'self'; script-src 'self'\n```\n\n3. **Input validation**: If possible, validate and sanitize ProseMirror documents before conversion to prevent malicious content from entering the system.\n\n### References\n\n- Vulnerable code: https://github.com/etaminstudio/prosemirror_to_html/blob/ea8beb32f6c37f29f042ba4155ccf18504da716e/lib/prosemirror_to_html.rb#L249\n- [OWASP XSS Prevention Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html)\n- [CWE-79: Improper Neutralization of Input During Web Page Generation](https://cwe.mitre.org/data/definitions/79.html)","aliases":["CVE-2025-64501"],"modified":"2026-02-03T03:08:25.970585Z","published":"2025-11-06T15:44:35Z","database_specific":{"nvd_published_at":"2025-11-10T22:15:37Z","cwe_ids":["CWE-79"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2025-11-06T15:44:35Z"},"references":[{"type":"WEB","url":"https://github.com/etaminstudio/prosemirror_to_html/security/advisories/GHSA-52c5-vh7f-26fx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-64501"},{"type":"WEB","url":"https://github.com/etaminstudio/prosemirror_to_html/commit/4d59f94f550bcabeec30d298791bbdd883298ad8"},{"type":"PACKAGE","url":"https://github.com/etaminstudio/prosemirror_to_html"},{"type":"WEB","url":"https://github.com/etaminstudio/prosemirror_to_html/blob/ea8beb32f6c37f29f042ba4155ccf18504da716e/lib/prosemirror_to_html.rb#L249"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/prosemirror_to_html/CVE-2025-64501.yml"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/prosemirror_to_html/GHSA-vfpf-xmwh-8m65.yml"}],"affected":[{"package":{"name":"prosemirror_to_html","ecosystem":"RubyGems","purl":"pkg:gem/prosemirror_to_html"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.2.1"}]}],"versions":["0.1.0","0.2.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2025/11/GHSA-52c5-vh7f-26fx/GHSA-52c5-vh7f-26fx.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N"}]}