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Vulnerabilities

Vulnerability · CVE-2021-47857

Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts.

Published Jan 21, 2026 · catalog updated Jun 17, 2026 · Moodle 3.10.3 contains a

Last checked Nov 4, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2021-47857. EPSS is 0.38%. Act only if a listed version of Moodle 3.10.3 contains a is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Moodle 3.10.3 contains a).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium5.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.38%
Remediation
Vendor / distro source
Affected products
cpe moodle/moodle · vendor Moodle Moodle 3.10.3

Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when users view the event.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe moodle/moodle3.10.3
  • vendor Moodle Moodle 3.10.33.10.3

How to fix CVE-2021-47857

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-47857. EPSS is 0.38%. Act only if a listed version of Moodle 3.10.3 contains a is installed.

Which versions are affected?

Compare what you have installed with Moodle Moodle 3.10.3 3.10.3. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.38%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Moodle security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jan 21, 2026 · EUVD

    Detected

    Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when users view the event.

  2. Mar 5, 2026 · EUVD

    Updated

    Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when users view the event.

  3. Jun 17, 2026 · Monitored products — high

    Updated

    Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when users view the event.

Sources

  • CVE.orgVulnerability recordCVE-2021-47857

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-47857

    30-day exploitation probability 0.38%

    first.org
  • EUVDVulnerability recordEUVD-2026-3616

    Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when

    euvd.enisa.europa.eu
  • Monitored products — highVendor advisoryCVE-2021-47857

    Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when users view the event.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • Monitored products — highNov 4, 2026
  • CVE.orgNov 4, 2026
  • FIRST EPSSNov 3, 2026
  • EUVDNov 2, 2026