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MEDIUM severity

Gon gem lack of escaping certain input when outputting as JSONGHSA-78vq-9j56-wrfr

MEDIUMFix: gazay/gon@fe3c7b2

GHSA-78vq-9j56-wrfr is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in gon. A fix is available for gon — see the affected versions and patch details below.

Also known asCVE-2020-25739
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs71th percentile — riskier than 71% of all scored CVEsHighest risk
0.11%0.70%1.29%1.88%0.8%1.4%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-78vq-9j56-wrfr by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 386,684 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
💎gon

Real-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

An issue was discovered in the gon gem before gon-6.4.0 for Ruby. MultiJson does not honor the escape_mode parameter to escape fields as an XSS protection mechanism. To mitigate, json_dumper.rb in gon now does escaping for XSS by default without relying on MultiJson.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemsgonall versions6.4.0bundle update gon --conservative

Affected Products

3 products · 3 configurations
OS
ubuntu linuxcanonical
1 version
18.04
OS
debian linuxdebian
1 version
9.0
Application
gongon_project
< 6.4.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for gon, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update gon to 6.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-78vq-9j56-wrfr is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

UbuntuMEDIUM
USN-4560-1Ubuntu

Frequently Asked Questions

An issue was discovered in the gon gem before gon-6.4.0 for Ruby. MultiJson does not honor the escape_mode parameter to escape fields as an XSS protection mechanism. To mitigate, json_dumper.rb in gon now does escaping for XSS by default without relying on MultiJson.
O3 Security · Impact-Aware SCA

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