CVE-2021-28145Public exploitNetwork attack vector

Stored XSS via unsanitized survey content

Published Mar 18, 2021 · Updated Aug 3, 2024

Stored XSS in the survey block in Concrete CMS before 8.5.5 allows remote authenticated users to execute JavaScript in reviewers' browsers. Survey content is stored and rendered in Reports > Surveys without neutralizing embedded JavaScript, so reviewing results executes the payload. At least Editor privileges are required to plant the payload, and execution requires another user to review survey results; the published impact is limited to that user's browser session.

CVSS severity5.4
Medium
EPSS probability0.86%
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 the survey block in Concrete CMS before 8.5.5 allows remote authenticated users to execute JavaScript in reviewers' browsers. Survey content is stored and rendered in Reports > Surveys without neutralizing embedded JavaScript, so reviewing results executes the payload. At least Editor privileges are required to plant the payload, and execution requires another user to review survey results; the published impact is limited to that user's browser session.

The record

CVE
CVE-2021-28145
Published
Mar 18, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 18, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.4GitHub Advisory DatabaseCVSS: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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

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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