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Not in CISA KEV
HIGH severity

CVE-2019-10905 — parsedown

HIGH

CVE-2019-10905 is a high-severity (CVSS 8.1) Cross-site Scripting (XSS) vulnerability in erusev/parsedown. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for erusev/parsedown — see the affected versions and patch details below.

Parsedown Class-Name Injection

Also known asGHSA-62m3-fc7f-jpp8
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs74th percentile — riskier than 74% of all scored CVEsHighest risk
0.02%0.67%1.32%1.97%0.5%1.5%May 26Sep 26Nov 26

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐘erusev/parsedown

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

Description

Parsedown before 1.7.2, when safe mode is used and HTML markup is disabled, might allow attackers to execute arbitrary JavaScript code if a script (already running on the affected page) executes the contents of any element with a specific class. This occurs because spaces are permitted in code block infostrings, which interferes with the intended behavior of a single class name beginning with the language- substring.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagisterusev/parsedownall versions1.7.2composer require erusev/parsedown:^1.7.2

Affected Products

1 product · 1 configurations
Application
parsedownparsedown
< 1.7.2
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.

Parsedown before 1.7.2, when safe mode is used and HTML markup is disabl…

github.comNVDAug 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 erusev/parsedown, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update erusev/parsedown to 1.7.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-10905 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

Parsedown before 1.7.2, when safe mode is used and HTML markup is disabled, might allow attackers to execute arbitrary JavaScript code if a script (already running on the affected page) executes the contents of any element with a specific class. This occurs because spaces are permitted in code block infostrings, which interferes with the intended behavior of a single class name beginning with the language- substring.
O3 Security · Impact-Aware SCA

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CVE-2019-10905: parsedown — Fixed in 1.7.2