https://www.hacker101.com/resources# https://www.bugcrowd.com/resources/levelup/ https://hackerone.com/hacktivity/overview?queryString=severity_rating%3A%28%22Critical%22+OR+%22High%22+OR+%22Medium%22%29+AND+disclosed%3Atrue&sortField=latest_disclosable_activity_at&sortDirection=DESC&pageIndex=0