In May 2014, the Avast anti-virus forum was hacked and 423k member records were exposed online.
The Simple Machines Based forum included usernames, email addresses and password hashes of about 422,959 individuals.
Source: https://haveibeenpwned.com/PwnedWebsites#Avast
"id": "AVA221624123",
"linkid": "avast",
"type": "Data Leak",
"date": "05/2014",
"severity": "60",
"impact": "3",
"explanation": "Attack with significant impact with internal employee data leaks"