CVE-2026-55872 GYM One admin user list is vulnerable to stored cross-site scripting
Attackers can inject malicious scripts into user profile fields, which execute in administrators' browsers, potentially leading to session hijacking or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-55872?
CVE-2026-55872 is a high-severity cross-site scripting vulnerability in mayerbalintdev GYM-One, published on 15 Oct 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-55872?
How do I fix CVE-2026-55872?
No fix has been published for CVE-2026-55872 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55872 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55872 exists.
Sources
Also known as GHSA-75g9-vp9w-5388.