CVE-2021-20183Network attack vector

Victim-side script execution via unescaped search query

Published Jan 28, 2021 · Updated Aug 3, 2024

Reflected XSS in Moodle LMS before 3.10.1 allows remote attackers to execute script in a victim's browser through a crafted search query. The lib/templates/search_input.mustache template renders the query value with a triple-brace Mustache expression that suppresses HTML escaping. No authentication is required to supply the query, but a victim must open the resulting page; execution is confined to that victim's browser context.

CVSS severity5.4
Medium
EPSS probability0.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Moodle LMS before 3.10.1 allows remote attackers to execute script in a victim's browser through a crafted search query. The lib/templates/search_input.mustache template renders the query value with a triple-brace Mustache expression that suppresses HTML escaping. No authentication is required to supply the query, but a victim must open the resulting page; execution is confined to that victim's browser context.

The record

CVE
CVE-2021-20183
Published
Jan 28, 2021
Updated
Aug 3, 2024
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 28, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=moodle 3.10.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Moodle · Moodle LMSversion=moodle 3.10.1

Published CVSS scores

5.4Canonical UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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