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MEDIUM severity

Moodle vulnerable to Stored Cross-site ScriptingGHSA-g6h6-4fp6-w33w

MEDIUM

GHSA-g6h6-4fp6-w33w is a medium-severity (CVSS 4.8) Cross-site Scripting (XSS) vulnerability in moodle/moodle. A fix is available for moodle/moodle — see the affected versions and patch details below.

Also known asBIT-moodle-2021-36401CVE-2021-36401
Published
Updated
Affected
3 pkgs
Patched
3 / 3
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-g6h6-4fp6-w33w.

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs45th percentile — riskier than 45% of all scored CVEsHighest risk
0.00%0.34%0.69%1.03%0.2%0.5%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

3 pkgs affected
🐘moodle/moodle🐘moodle/moodle🐘moodle/moodle

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

In Moodle, ID numbers exported in HTML data formats required additional sanitizing to prevent a local stored XSS risk.

Affected Packages

3 total 3 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistmoodle/moodle≥ 3.11.0-beta&&< 3.11.13.11.1composer require moodle/moodle:^3.11.1
🐘Packagistmoodle/moodle≥ 3.10.0-beta&&< 3.10.53.10.5composer require moodle/moodle:^3.10.5
🐘Packagistmoodle/moodleall versions3.9.8composer require moodle/moodle:^3.9.8

Affected Products

1 product · 3 configurations
Application
moodlemoodle
≥ 3.11.0 && < 3.11.1
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 moodle/moodle, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update moodle/moodle to 3.11.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g6h6-4fp6-w33w 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

In Moodle, ID numbers exported in HTML data formats required additional sanitizing to prevent a local stored XSS risk.
O3 Security · Impact-Aware SCA

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Moodle vulnerable to Stored Cross-site Scripting