GHSA-52c5-vh7f-26fx
HIGHCross-Site Scripting (XSS) vulnerability through unescaped HTML attribute values
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
prosemirror_to_htmlReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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:
hrefattributes withjavascript:protocol:<a href="javascript:alert(document.cookie)">- Event handlers:
<div onclick="maliciousCode()"> onerrorattributes 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 injection attacks.
Workarounds
Until a patched version is available, users can implement one or more of these mitigations:
html = ProsemirrorToHtml.render(document)
safe_html = Sanitize.fragment(html, Sanitize::Config::RELAXED)
- Implement Content Security Policy (CSP): Add strict CSP headers to prevent inline JavaScript execution:
Content-Security-Policy: default-src 'self'; script-src 'self'
- Input validation: If possible, validate and sanitize ProseMirror documents before conversion to prevent malicious content from entering the system.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | prosemirror_to_html | all versions | 0.2.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for prosemirror_to_html. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update prosemirror_to_html to 0.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-52c5-vh7f-26fx is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-52c5-vh7f-26fx is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-52c5-vh7f-26fx. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-52c5-vh7f-26fx in your dependencies?
O3 detects GHSA-52c5-vh7f-26fx across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.