GHSA-52c5-vh7f-26fx: Cross-Site Scripting (XSS) vulnerability through unescaped HTML attribute values

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.

Who is impacted:

• Any application using prosemirror_to_html 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