CVE-2026-55872

HIGH 8.7

GYM One admin user list is vulnerable to stored cross-site scripting

CVSS Score

8.7

EPSS Score

0.0%

EPSS Percentile

0th

GYM One is open-source gym management software for fitness centers, personal trainers, and sports clubs. Prior to 1.4.1, GYM One's admin/users/index.php renders the stored firstname, lastname, and email profile fields into the administrator user list without HTML output encoding. An attacker who can store values in those fields can cause content to execute in an administrator's browser when the administrator visits /admin/users/. The persistent script can access administrator-session data or perform actions with the administrator's privileges until the stored record is removed. This issue is fixed in version 1.4.1.

CWE	CWE-79
Vendor	mayerbalintdev
Product	gym-one
Published	Oct 15, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Affected Versions

mayerbalintdev / GYM-One

< 1.4.1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/mayerbalintdev/GYM-One/security/advisories/GHSA-75g9-vp9w-5388 github.com: https://github.com/mayerbalintdev/GYM-One/commit/d3a0cf134f0ab3ac12aee7dca283b93c4290dcc4 github.com: https://github.com/mayerbalintdev/GYM-One/releases/tag/V1.4.1