A group of hackers claim to have exploited an undocumented vulnerability in the vBulletin Internet forum software in order to break into the MacRumors.com and vBulletin.com forums.
On Friday, vBulletin Solutions, the company behind the vBulletin software, reset the passwords for all accounts on the vBulletin.com support forums after confirming that hackers broke into its systems and stole customer log-in credentials.
"Very recently, our security team discovered sophisticated attacks on our network, involving the illegal access of forum user information, possibly including your password," Wayne Luke, the technical support lead at vBulletin Solutions, said in a message posted on the forum. "Our investigation currently indicates that the attackers accessed customer IDs and encrypted passwords on our systems."
Luke advised users to choose a new password that they're not using on any other websites.
The announcement came a day after a group of hackers calling themselves the Inj3ct0r Team announced in a post on Facebook that they compromised the vBulletin.com and MacRumors.com forums.
Inj3ct0r Team claims to have found and exploited a previously unknown -- zero-day -- remote code execution vulnerability affecting all versions of vBulletin 4 and 5 and which allowed them to upload a Web shell on the vBulletin.com server, gain root access to it and download the site's database.
VBulletin Solutions did not immediately respond to a request for comment regarding the claims of a zero-day vulnerability existing in vBulletin.
The hackers said they exploited the same vulnerability to obtain the password of a moderator on the MacRumors.com forum, which uses the vBulletin software, allowing them to obtain the log-in credentials for that forum's 860,000 users.
The MacRumors.com administrators announced Tuesday that the site had been compromised and warned their users that "while the passwords are 'hashed' (which is a one-way conversion from your actual password to a scrambled version), given computing power these days, if your password isn't very complex, they could brute force figure it out by trying lots of combinations."
Inj3ct0r Team put the new vBulletin exploit up for sale on its website for the equivalent of US$7,000 payable through WebMoney or Bitcoin. Ironically, the hackers say on their website that "we don't want you to use our site as a tool for hacking purposes, so any kind of action that could affect illegally other users or websites that you don't have right to access will be banned and your account including your data will be destroyed."
Some website administrators have already reacted to the news. The community forums for the DefCon hacking conference have been temporarily shut down, with administrators informing users that "we have disabled the forums until there is resolution on a possible vulnerability."
According to vBulletin Solutions, over 100,000 community websites are running on vBulletin, including some operated by Zynga, Electronic Arts, Sony Pictures, NASA, Valve Corporation and other well known companies.
UbuntuForums.org, a community website for the Ubuntu Linux distribution with over 1.8 million registered accounts, is also using vBulletin and was hacked back in July. The MacRumors administrators described the recent compromise of their forum as similar to the UbuntuForums.org hack.