CVE-2026-86244A security vulnerability has been detected in FastAdmin up to 1.2.0.20210401_beta. Affected is the function register/login of the file application/index/controller/User.php of the component User Controller. Such manipulation of the argument url leads to cross site scripting. The attack may be performed from remote. The exploit has been disclosed publicly and may be used. Upgrading to version 1.2.1.20210731_beta is able to address this issue. The name of the patch is b3d32e2bf3637488cfe2fc58a27a9d2475b2b51b. It is recommended to upgrade the affected component.