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MEDIUM severity

CVE-2020-13973 — json-sanitizer

MEDIUMFix: OWASP/json-sanitizer#20

CVE-2020-13973 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in com.mikesamuel:json-sanitizer. 1 public exploit reference exists, so weaponization risk is real. A fix is available for com.mikesamuel:json-sanitizer — see the affected versions and patch details below.

Cross-site scripting in json-sanitizer

Also known asGHSA-g8jj-899q-8x3j
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.1%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs65th percentile — riskier than 65% of all scored CVEsHighest risk
0.00%0.54%1.08%1.62%0.5%1.1%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-13973 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 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
☕com.mikesamuel:json-sanitizer

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

OWASP json-sanitizer before 1.2.1 allows XSS. An attacker who controls a substring of the input JSON, and controls another substring adjacent to a SCRIPT element in which the output is embedded as JavaScript, may be able to confuse the HTML parser as to where the SCRIPT element ends, and cause non-script content to be interpreted as JavaScript.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavencom.mikesamuel:json-sanitizerall versions1.2.1com.mikesamuel:json-sanitizer:1.2.1

Affected Products

1 product · 1 configurations
Application
json-sanitizerowasp
< 1.2.1
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

OWASP json-sanitizer before 1.2.1 allows XSS. An attacker who controls a…

github.comNVDJun 2020

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update com.mikesamuel:json-sanitizer to 1.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-13973 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.

Frequently Asked Questions

OWASP json-sanitizer before 1.2.1 allows XSS. An attacker who controls a substring of the input JSON, and controls another substring adjacent to a SCRIPT element in which the output is embedded as JavaScript, may be able to confuse the HTML parser as to where the SCRIPT element ends, and cause non-script content to be interpreted as JavaScript.
O3 Security · Impact-Aware SCA

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CVE-2020-13973: json-sanitizer XSS — Fixed in 1.2.1