CVE-2020-21387Public exploitNetwork attack vector

Administrator session theft via unsanitized type_en rendering

Published Oct 4, 2021 · Updated Aug 4, 2024

Cross-site scripting in MacCMS 10 allows remote attackers to steal an administrator cookie through a crafted type_en value. The classification endpoint stores type_en as an English name without neutralizing quotation marks and event-handler syntax, causing the payload to execute on mouseover. An administrator must open attacker-controlled HTML and interact with the injected value; script execution exposes the session cookie and administrator privileges.

CVSS severity6.1
Medium
EPSS probability0.57%
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 MacCMS 10 allows remote attackers to steal an administrator cookie through a crafted type_en value. The classification endpoint stores type_en as an English name without neutralizing quotation marks and event-handler syntax, causing the payload to execute on mouseover. An administrator must open attacker-controlled HTML and interact with the injected value; script execution exposes the session cookie and administrator privileges.

The record

CVE
CVE-2020-21387
Published
Oct 4, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 4, 2021CVE 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1539Steal Web Session Cookie

Public exploit references

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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