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October CMS: Reflected XSS via DataTable Form Widget

Low severity GitHub Reviewed Published Apr 21, 2026 in octobercms/october • Updated Apr 24, 2026

Package

composer october/system (Composer)

Affected versions

< 3.7.16
>= 4.0.0, < 4.1.16

Patched versions

3.7.16

Description

A reflected Cross-Site Scripting (XSS) vulnerability was identified in the backend DataTable widget where a query parameter was rendered without proper output escaping.

Impact

  • Reflected XSS only, no stored/persistent component
  • The backend URL prefix is customizable and must be known or guessed by the attacker
  • Requires an authenticated backend user to visit a crafted URL
  • No direct access is gained without social engineering

Patches

The vulnerability has been patched in v3.7.16 and v4.1.16. The affected parameter is now properly escaped. All users are encouraged to upgrade to the latest patched version.

Workarounds

  • Use a non-default backend URL prefix (recommended as standard practice)
  • Implement a Content Security Policy (CSP) for backend pages

References

@daftspunk daftspunk published to octobercms/october Apr 21, 2026
Published to the GitHub Advisory Database Apr 21, 2026
Reviewed Apr 21, 2026
Published by the National Vulnerability Database Apr 21, 2026
Last updated Apr 24, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(4th percentile)

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

CVE ID

CVE-2026-27937

GHSA ID

GHSA-jj38-h5w5-mvpf

Source code

Credits

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