CVE-2023-28331Network attack vector

Browser script execution via unescaped link titles

Published Mar 23, 2023 · Updated Feb 25, 2025

Cross-site scripting in Moodle LMS before 3.9.20 and affected 3.11, 4.0, and 4.1 releases allows remote attackers to execute browser script. The database auto-linking filter in filter/data/filter.php inserted database-entry content into an anchor title attribute without applying s() HTML escaping. A victim must view filtered database-activity content; injected script then runs in the victim's browser, enabling limited data access or modification in that context.

CVSS severity6.1
Medium
EPSS probability0.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Moodle LMS before 3.9.20 and affected 3.11, 4.0, and 4.1 releases allows remote attackers to execute browser script. The database auto-linking filter in filter/data/filter.php inserted database-entry content into an anchor title attribute without applying s() HTML escaping. A victim must view filtered database-activity content; injected script then runs in the victim's browser, enabling limited data access or modification in that context.

The record

CVE
CVE-2023-28331
Published
Mar 23, 2023
Updated
Feb 25, 2025
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 23, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 2025Record 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=0 <3.9.20
  2. Affected versionversion=3.11.0 <3.11.13
  3. Affected versionversion=4.0.0 <4.0.7
  4. Affected versionversion=4.1.0 <4.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Moodle · Moodle LMSversion=0 <3.9.20; version=3.11.0 <3.11.13; version=4.0.0 <4.0.7; version=4.1.0 <4.1.2

Published CVSS scores

6.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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')
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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