baserCMS is a website development framework. Starting in version 5.0.0-beta1 and prior to versions 5.3.2 and 5.4.2, "PermissionGroupsService::build()" reads a plugin's "config/permission.php" to decide what each user group may reach. When that file is absent it writes a wildcard allow rule instead: "url" "/baser/<prefix>/<plugin>/*", "method" "*", "auth" true, for every non-admin group. BcCustomContent has no such file in any release. After an administrator installs it, the default "operators" group can store and execute arbitrary PHP under the document root. Versions 5.3.2 and 5.4.2 patch the issue.