I just receive a malware warning from my web host 20i.com. I have had this app installed for quite a few months and it's the first time I have seen this. Is this a real threat? How do I deal with this? Any advice would be greatly appreciated...

Filename: phpstan.phar
Path: /home/sites/33a/e/eec892f2d0/public_html/vendor/phpstan/phpstan/phpstan.phar
Exploit: php.eval.str.replace.cookie.array.array.base64.decode