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Not in CISA KEV
MEDIUM severity

CVE-2020-11888 — markdown2

MEDIUM

CVE-2020-11888 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in markdown2. 1 public exploit reference exists, so weaponization risk is real. A fix is available for markdown2 — see the affected versions and patch details below.

XSS in python-markdown2

Also known asGHSA-fv3h-8x5j-pvgqPYSEC-2020-65
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk
0.15%0.91%1.67%2.43%0.7%1.9%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-11888 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 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
🐍markdown2

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

Description

python-markdown2 through 2.3.8 allows XSS because element names are mishandled unless a \w+ match succeeds. For example, an attack might use elementname@ or elementname- with an onclick attribute.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPImarkdown2all versions2.3.9pip install --upgrade 'markdown2==2.3.9'

Affected Products

1 product · 1 configurations
Application
python-markdown2python-markdown2_project
≤ 2.3.8
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.

python-markdown2 through 2.3.8 allows XSS because element names are mish…

github.comNVDMay 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 markdown2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update markdown2 to 2.3.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-11888 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

python-markdown2 through 2.3.8 allows XSS because element names are mishandled unless a \w+ match succeeds. For example, an attack might use elementname@ or elementname- with an onclick attribute.
O3 Security · Impact-Aware SCA

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CVE-2020-11888: markdown2 XSS — Fixed in 2.3.9