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MEDIUM severity

CVE-2021-36568 — moodle

MEDIUM

CVE-2021-36568 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in moodle/moodle. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for moodle/moodle — see the affected versions and patch details below.

Moodle Cross-site Scripting vulnerability

Also known asBIT-moodle-2021-36568GHSA-fm6m-fg23-67jq
Published
Updated
Affected
3 pkgs
Patched
1 / 3
Exploits
1 known
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.1%probability of exploitation in next 30 days
Lower Risk+0.02%
Lower risk than most CVEs65th percentile — riskier than 65% of all scored CVEsHighest risk
0.00%0.52%1.04%1.57%0.4%1.1%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 certain Moodle products after creating a course, it is possible to add in a arbitrary "Topic" a resource, in this case a "Database" with the type "Text" where its values "Field name" and "Field description" are vulnerable to Cross Site Scripting Stored(XSS). This affects Moodle 3.11.x prior to 3.11.10, Moodle 3.10.4, and Moodle 3.9.7.

Affected Packages

3 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistmoodle/moodleall versionsNo fix
🐘Packagistmoodle/moodle≥ 3.10.0No fix
🐘Packagistmoodle/moodle≥ 3.11.0&&< 3.11.103.11.10composer require moodle/moodle:^3.11.10

Affected Products

2 products · 5 configurations
OS
fedorafedoraproject
2 versions
3536
Application
moodlemoodle
3 versions
3.9.73.10.43.11.0
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.

In certain Moodle products after creating a course, it is possible to ad…

blog.hackingforce.com.brNVDSep 2022

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

    A fix is available for CVE-2021-36568; check the affected-versions list above or the advisory for the patched release of moodle/moodle, then make sure no transitive dependency still pins the vulnerable range.

  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 certain Moodle products after creating a course, it is possible to add in a arbitrary "Topic" a resource, in this case a "Database" with the type "Text" where its values "Field name" and "Field description" are vulnerable to Cross Site Scripting Stored(XSS). This affects Moodle 3.11.x prior to 3.11.10, Moodle 3.10.4, and Moodle 3.9.7.
O3 Security · Impact-Aware SCA

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CVE-2021-36568: moodle XSS — Fixed in 3.11.10