How severe is CVE-2021-20279?

CVE-2021-20279 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-20279?

CVE-2021-20279 affects the following packages: moodle/moodle (Packagist), moodle/moodle (Packagist), moodle/moodle (Packagist), moodle/moodle (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-20279?

Update moodle/moodle to 3.10.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20279 is resolved across your whole dependency graph.

How do I detect CVE-2021-20279 in my Packagist dependencies?

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.

How do I mitigate CVE-2021-20279 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-20279 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-20279 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-20279?

CVE-2021-20279 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 63th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-20279?

CVE-2021-20279 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-20279 published, and has it been updated?

CVE-2021-20279 was published on March 15, 2021 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

MEDIUM severity

CVE-2021-20279 — moodle

MEDIUMFix: moodle/moodle@a7e0ba1

CVE-2021-20279 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in moodle/moodle. A fix is available for moodle/moodle — see the affected versions and patch details below.

Moodle contains Stored XSS via ID number user profile field

Also known asBIT-moodle-2021-20279GHSA-h7h6-fwpv-ggvx

Published

Mar 15, 2021

Updated

Oct 24, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs63th percentile — riskier than 63% of all scored CVEsHighest risk

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

4 pkgs affected

🐘moodle/moodle🐘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

The ID number user profile field required additional sanitizing to prevent a stored XSS risk in moodle before 3.10.2, 3.9.5, 3.8.8, 3.5.17.

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`moodle/moodle`	≥ 3.10&&< 3.10.2	3.10.2`composer require moodle/moodle:^3.10.2`
🐘Packagist	`moodle/moodle`	≥ 3.9&&< 3.9.5	3.9.5`composer require moodle/moodle:^3.9.5`
🐘Packagist	`moodle/moodle`	≥ 3.8&&< 3.8.8	3.8.8`composer require moodle/moodle:^3.8.8`
🐘Packagist	`moodle/moodle`	≥ 3.5&&< 3.5.17	3.5.17`composer require moodle/moodle:^3.5.17`

Affected Products

2 products · 6 configurations

fedorafedoraproject

2 versions

3234

Application

moodlemoodle

≥ 3.10.0 && < 3.10.2

range

Detection & mitigation playbook

Open-source dependency

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.
Fix
Update moodle/moodle to 3.10.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20279 is resolved across your whole dependency graph.
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

The ID number user profile field required additional sanitizing to prevent a stored XSS risk in moodle before 3.10.2, 3.9.5, 3.8.8, 3.5.17.

O3 Security · Impact-Aware SCA

Is CVE-2021-20279 in your dependencies?

Find it across Packagist, including transitive dependencies.

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CVSS Score

5.4/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

OpenSSF Scorecard

Package health score

moodle

3.4/10

Code-Review0/10

Maintained10/10

Branch-Protection0/10

Assessed Oct 26, 2026

Timeline

Disclosed

Mar 15, 2021

Last updated

Oct 24, 2026

Identifiers

CVE-2021-20279

GHSA-h7h6-fwpv-ggvx

BIT-moodle-2021-20279

References

Advisorynvd.nist.gov · CVE 2021 20279 Fixmoodle.org · discuss Reportbugzilla.redhat.com · show bug.cgi Weblists.fedoraproject.org · AFSNJ7XHVTC52RSRX2GBQFF3VEEAY2MS Weblists.fedoraproject.org · UFH5DDMU5TZ3JT4Q52WMRAHACA5MHIMT Webgithub.com · a7e0ba1e71205ccb0a73dedee414f1a167ee2ed7 Weblists.fedoraproject.org · AFSNJ7XHVTC52RSRX2GBQFF3VEEAY2MS Weblists.fedoraproject.org · UFH5DDMU5TZ3JT4Q52WMRAHACA5MHIMT

Related vulnerabilities

This CVE is medium severity; 8 of 8 other CVEs affecting moodle/moodle are rated as high or higher (top: high).

CVE-2026-26047CVE-2026-26045CVE-2025-67853CVE-2025-67850CVE-2025-67857CVE-2025-67856CVE-2025-67848CVE-2025-67849

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026