Avast Support: Submitting Malware Samples https://www.avast.com/faq.php?article=AVKB258#artTitle
Submitting False Positive https://www.avast.com/false-positive-file-form.php
Submitting files from the Virus Chest to Avast Virus Lab https://www.avast.com/faq.php?article=AVKB21#idt_07
Report a URL https://www.avast.com/report-a-url.php