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Vulnerability record · CVE-2021-23838 · published 15 January 2021

CVE-2021-23838: Flatcore cross-site scripting vulnerability

Flatcore · Flatcore

An issue was discovered in flatCore before 2.0.0 build 139. A reflected XSS vulnerability was identified in the media_filter HTTP request body parameter for the acp interface. The affected parameter accepts malicious client-side script without proper input sanitization. For example, a malicious user can leverage this vulnerability to steal cookies from a victim user and perform a session-hijacking attack, which may then lead to unauthorized access to the site.

4.8 CVSS 3.1 Medium EPSS 0.98% · top 39.3% CWE-79 · Cross-site scripting
4.8CVSS 3.1 base score, v2 3.5
0.98%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

An issue was discovered in flatCore before 2.0.0 build 139. A reflected XSS vulnerability was identified in the media_filter HTTP request body parameter for the acp interface. The affected parameter accepts malicious client-side script without proper input sanitization. For example, a malicious user can leverage this vulnerability to steal cookies from a victim user and perform a session-hijacking attack, which may then lead to unauthorized access to the site.

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://packetstormsecurity.com/files/160936/flatCore-CMS-XSS-File-Disclosure-SQL-Injection.html ExploitThird Party AdvisoryVDB Entry
https://github.com/flatCore/flatCore-CMS ProductThird Party Advisory
https://sec-consult.com/vulnerability-lab/ Third Party Advisory
http://packetstormsecurity.com/files/160936/flatCore-CMS-XSS-File-Disclosure-SQL-Injection.html ExploitThird Party AdvisoryVDB Entry
https://github.com/flatCore/flatCore-CMS ProductThird Party Advisory
https://sec-consult.com/vulnerability-lab/ Third Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.8CVE-2019-13961Flatcore cross-site request forgery vulnerabilityA CSRF vulnerability was found in flatCore before 1.5, leading to the upload of arbitrary .php files via acp/core/files.upload-script.php.EPSS 2.3%7.2CVE-2020-17452Flatcore unrestricted file upload vulnerabilityflatCore before 1.5.7 allows upload and execution of a .php file by an admin.EPSS 2.4%7.2CVE-2019-10652Flatcore unrestricted file upload vulnerabilityAn issue was discovered in flatCore 1.4.7. acp/acp.php allows remote authenticated administrators to upload arbitrary .php files, related to the addo…EPSS 7.0%6.5CVE-2021-23837Flatcore sql injection vulnerabilityAn issue was discovered in flatCore before 2.0.0 build 139. A time-based blind SQL injection was identified in the selected_folder HTTP request body …EPSS 1.5%6.1CVE-2017-9451Flatcore cross-site scripting vulnerabilityCross site scripting (XSS) vulnerability in pages.edit_form.php in flatCore 1.4.6 allows remote attackers to inject arbitrary JavaScript via the PATH…EPSS 0.74%5.4CVE-2021-40555Flatcore cross-site scripting vulnerabilityCross site scripting (XSS) vulnerability in flatCore-CMS 2.2.15 allows attackers to execute arbitrary code via description field on the new page crea…EPSS 0.44%4.9CVE-2021-23835Flatcore improper input validation vulnerabilityAn issue was discovered in flatCore before 2.0.0 build 139. A local file disclosure vulnerability was identified in the docs_file HTTP request body p…EPSS 1.7%4.8CVE-2021-23836Flatcore cross-site scripting vulnerabilityAn issue was discovered in flatCore before 2.0.0 build 139. A stored XSS vulnerability was identified in the prefs_smtp_psw HTTP request body paramet…EPSS 0.92%

Source: NIST National Vulnerability Database (record CVE-2021-23838), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.