Shopware: Privilege escalation: non-admin user with user:create ACL can create admin accounts

UserController::upsertUser() writes user data in SYSTEM_SCOPE and does not filter the admin field. A non-admin API user with user:create or user:update ACL permission can set admin: true on new or existing users, escalating to full admin access.

The Problem

In src/Core/Framework/Api/Controller/UserController.php, line 210-234:

public function upsertUser(?string $userId, Request $request, Context $context, ResponseFactoryInterface $factory): Response
{
    $data = $request->request->all(); // raw request data, no field filtering
    // ...
    $events = $context->scope(Context::SYSTEM_SCOPE, fn (Context $context) =>
        $this->userRepository->upsert([$data], $context)
    );
}

SYSTEM_SCOPE bypasses AclWriteValidator entirely (line 52 of AclWriteValidator::preValidate() returns early for SYSTEM_SCOPE). The admin boolean field is accepted without restriction.

Compare with IntegrationController::upsertIntegration() in the same codebase, which correctly checks:

if ((!$source instanceof AdminApiSource)
    || (!$source->isAdmin()
    && isset($data['admin']))
) {
    throw new PermissionDeniedException();
}

UserController is missing this exact check.

Impact

Any API user with the low-privilege user:create permission can create accounts with full admin access, or with user:update can promote any existing user to admin. This is a direct privilege escalation.

Suggested Fix

Add the same isAdmin() check from IntegrationController:

$source = $context->getSource();
if ((!$source instanceof AdminApiSource) || (!$source->isAdmin() && isset($data['admin']))) {
    throw new PermissionDeniedException();
}

Best regards, Keyvan Hardani