A Russian hacking group called W0rm is claiming to have stolen reader data from the technology website CNET, potentially affecting one million users.
Usernames, emails and passwords were said to have been taken from a database in the attack, which were later put on sale for 1 Bitcoin (£365) in what was claimed to be a publicity stunt.
W0rm said: "We are driven to make the Internet a better and safer [place] rather than [by] a desire to protect copyright.
"I want to note that the experts responsible for bezopastnost [security] in CNET [did] very good work but not without flaws."
A spokeswoman from the site's parent CBS Interactive confirmed that several servers were accessed, adding that the issue had been resolved "a few days ago".
W0rm said that they entered the site through a bug in the site's implementation of Symfony, a PHP framework used to programme complex websites.
It has previously claimed responsibility for an attack on the BBC at the end of last year, as well as hacking websites belonging to Adobe and the Bank of America.