CVE-2021-23838Public exploitNetwork attack vector

Session hijacking via unsanitized media filter input

Published Jan 15, 2021 · Updated Aug 3, 2024

Reflected XSS in flatCore CMS before 2.0.0 build 139 allows remote authenticated users to execute script via media_filter. The acp file-browser handler reflects the media_filter POST value without sanitizing malicious client-side script. Exploitation requires administrator access and victim interaction, enabling cookie theft and session hijacking that grants unauthorized site access.

CVSS severity4.8
Medium
EPSS probability0.98%
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 flatCore CMS before 2.0.0 build 139 allows remote authenticated users to execute script via media_filter. The acp file-browser handler reflects the media_filter POST value without sanitizing malicious client-side script. Exploitation requires administrator access and victim interaction, enabling cookie theft and session hijacking that grants unauthorized site access.

The record

CVE
CVE-2021-23838
Published
Jan 15, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1539, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jan 15, 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 privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
4.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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