CVE-2020-1691Network attack vector

Stored XSS via unsafe conversation preview

Published Aug 5, 2022 · Updated Aug 4, 2024

Stored XSS in Moodle LMS 3.8 allows remote authenticated users to execute script in another user's browser through a crafted message. The message drawer's conversation-overview preview returns text derived from lastMessage.text even when HTML or script markup remains. A logged-in user must send the crafted message and another user must load the conversation overview, enabling script execution in that viewer's session.

CVSS severity5.4
Medium
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Moodle LMS 3.8 allows remote authenticated users to execute script in another user's browser through a crafted message. The message drawer's conversation-overview preview returns text derived from lastMessage.text even when HTML or script markup remains. A logged-in user must send the crafted message and another user must load the conversation overview, enabling script execution in that viewer's session.

The record

CVE
CVE-2020-1691
Published
Aug 5, 2022
Updated
Aug 4, 2024
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 5, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=3.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Moodle · Moodle LMSversion=3.8

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
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.

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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