What’s Vulnerable › Vulnerabilities

CVE-2026-55872: GYM One admin user list is vulnerable to stored cross-site scripting

• Severity: high (CVSS 8.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-15 · updated 2026-10-21
• Weakness: CWE-79

Description

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.

Affected products

• mayerbalintdev GYM-One: before 1.4.1

References

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

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