{"id":"GHSA-4249-gjr8-jpq3","summary":"Duplicate Advisory: ProsemirrorToHtml has a Cross-Site Scripting (XSS) vulnerability through unescaped HTML attribute values","details":"## Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-52c5-vh7f-26fx. This link is maintained to preserve external references.\n\n## Original Description\n### 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\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\n- `href` attributes with `javascript:` protocol:\n  `\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. The 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\n   library like [Sanitize](https://github.com/rgrove/sanitize) or\n   [Loofah](https://github.com/flavorjones/loofah):\n\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\n   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\n   ProseMirror documents before conversion to prevent malicious\n   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)","modified":"2026-02-03T03:08:12.419257Z","published":"2025-11-13T22:59:15Z","withdrawn":"2026-01-23T23:00:51Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2025-11-13T22:59:15Z","nvd_published_at":null,"cwe_ids":["CWE-79"]},"references":[{"type":"WEB","url":"https://github.com/etaminstudio/prosemirror_to_html/security/advisories/GHSA-52c5-vh7f-26fx"},{"type":"WEB","url":"https://github.com/etaminstudio/prosemirror_to_html/commit/4d59f94f550bcabeec30d298791bbdd883298ad8"},{"type":"WEB","url":"https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html"},{"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/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-4249-gjr8-jpq3/GHSA-4249-gjr8-jpq3.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N"}]}