Cross-Site Scripting (XSS) vulnerability through unescaped HTML attribute values

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.6 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N

EPSS

• CVE-2025-64501: 0.24% estimated exploitation activity in the next 30 days; percentile 14.76 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The prosemirrortohtml 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. Who is impacted: - Any application using prosemirrortohtml to convert ProseMirror documents to HTML - Applications that process user-generated ProseMirror content are at highest risk - End users viewing the rendered HTML output could have malicious JavaScript executed in their browsers Attack vectors include: - href attributes with javascript: protocol: <a href="javascript:alert(document.cookie)" - Event handlers: <div onclick="maliciousCode()" - onerror attributes on images: <img src=x onerror="alert('XSS')" - Other HTML attributes that can execute JavaScript Patches A 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…

Published by the source

6 Nov 2025, 15:44 UTC

Last modified by the source

23 Jan 2026, 21:37 UTC

Source last checked

26 Oct 2026, 15:51 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-52c5-vh7f-26fx

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# Patch Next advisory brief: CVE-2025-64501

Advisory: Cross-Site Scripting (XSS) vulnerability through unescaped HTML attribute values
IDs: CVE-2025-64501, GHSA-52c5-vh7f-26fx
Record: https://patchnext.com/advisories/cve-2025-64501 (revision 1, source checked 26 Oct 2026, 15:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: prosemirror_to_html 0.2.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems prosemirror_to_html: affected < 0.2.1; fixed in 0.2.1

## Suggested inspection (read-only)
- RubyGems prosemirror_to_html: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on prosemirror_to_html.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-52c5-vh7f-26fx (GitHub-reviewed advisory GHSA-52c5-vh7f-26fx lists affected ranges: RubyGems prosemirror_to_html >=0 <0.2.1)

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