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CVE-2025-64501: ProsemirrorToHtml: Cross-Site Scripting vulnerability through unescaped HTML attribute values

• Severity: high (CVSS 7.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-11-10 · updated 2026-10-18
• Weakness: CWE-79

Description

ProsemirrorToHtml is a JSON converter which takes ProseMirror-compatible JSON and outputs HTML. In versions 0.2.0 and below, the `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. Applications that use `prosemirror_to_html` to convert ProseMirror documents to HTML, user-generated ProseMirror content, and end users viewing the rendered HTML output are all at risk of attack. This issue is fixed in version 0.2.1.

Affected products

• etaminstudio prosemirror_to_html: before 0.2.1

References

• https://github.com/etaminstudio/prosemirror_to_html/commit/4d59f94f550bcabeec30d298791bbdd883298ad8
• https://github.com/etaminstudio/prosemirror_to_html/security/advisories/GHSA-52c5-vh7f-26fx

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