False-positive on php composer installer

[juju4]

+Searching for Linux.Xor.DDoS ...                            INFECTED: Possible Malicious Linux.Xor.DDoS installed
+/tmp/composer-installer.php

$ sha256sum /tmp/composer-installer.php 
203196aedb1a3b0f563363796bbf6f647a4f8c2419bc1dfc5aa45adc1725025d  /tmp/composer-installer.php
$ dpkg -l |grep chkrootkit
ii  chkrootkit                                     0.55-4                                  amd64        rootkit detector
$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.3 LTS
Release:	22.04
Codename:	jammy

composer downloaded from https://getcomposer.org/installer and validated against https://getcomposer.org/installer.sig