Read the docs
TI-2026-74989 Aliases CVE-2026-55872

Stored cross-site scripting in GYM One admin user list

Priority HIGH 73CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Required
Attack complexity
Low
Impact type
Cross-site scripting
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

GYM One before 1.4.1 renders stored first name, last name and email profile fields into the administrator user list without HTML output encoding (CWE-79). An attacker who can store values in those fields can run script in an administrator's browser when the administrator visits /admin/users/. The script can access administrator session data or act with the administrator's privileges until the stored record is removed.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0029 21st percentileScored 2026-11-07
Fix Fixed GYM-One (mayerbalintdev): 1.4.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mayerbalintdevGYM-Onebefore 1.4.11.4.1Patch availableCNA
  • GYM-One Vendormayerbalintdev Affected before 1.4.1 Fixed in 1.4.1 Patch available CNA

Remediation

Upgrade GYM One to version 1.4.1, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA GYM-One (mayerbalintdev) Fixed in 1.4.1

Timeline

  1. 2026-10-16 Threatist record created from CVE-2026-55872
  2. 2026-10-16 Priority changed: MEDIUM → LOW
  3. 2026-10-21 CISA SSVC decision points changed
  4. 2026-10-21 Priority changed: LOW → HIGH

References

Other 3

  • TI-2026-74988 SQL injection in GYM One admin user search CVSS 3.1MEDIUM 6.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences