
According to Internet Archive founder Brewster Kahle and 'Have I been Pwned?' founder Troy Hunt via Bleeping Computer The Internet Archive was hacked. Resulting in a data breach of its user authentication database containing 31 million accounts. Users found out when they saw the website displaying a JavaScript alert to let visitors know the site was breached. Along with the data breach, the website was defaced and DDoS'd (Distributed Denial of Service).
The following was the message on the pop-up: