The PHP Group will reset the passwords for accounts on php.net, the official website of the PHP programming language, and will change the site's SSL certificate after attackers compromised two servers and injected malicious code into the website.
The security breach was confirmed Thursday after earlier in the day the Google Safe Browsing service blacklisted the site for distributing malware, which caused Mozilla Firefox and Google Chrome to block users from visiting it.
The PHP Group's investigation, which is still in progress, revealed that the compromise extended to two servers: the server that hosted the www.php.net, static.php.net and git.php.net domains and the server that hosted bugs.php.net, the project's bug tracking system.
There is no evidence that the PHP distribution packages or the Git repository used for source code management have been compromised.
"All affected services have been migrated off those servers," the PHP Group said in a status update. "We have verified that our Git repository was not compromised, and it remains in read only mode as services are brought back up in full."
The method used by attackers to compromise the two servers and inject rogue code into userprefs.js has yet to be determined.
Php.net users who contribute to different projects hosted on svn.php.net or git.php.net will have their passwords reset, the PHP Group said.
In addition, the SSL certificate used on several php.net websites has been revoked, because it's possible that attackers might have gained access to the certificate's private key.
"We are in the process of getting a new certificate, and expect to restore access to php.net sites that require SSL (including bugs.php.net and wiki.php.net) in the next few hours," the PHP Group said.
Users who visited the affected php.net websites between Oct. 22 and Oct. 24 should scan their computers for malware.
The malicious code was only intermittently served to users during that time because an existing synchronization process was periodically reverting the userprefs.js to its original clean state. As a result, not all visitors were affected, but it's hard to know which ones were.
According to security researchers from Alien Vault, the malicious code on php.net loaded an instance of the Magnitude exploit kit hosted on a different website. Exploit kits are Web-based attack tools that exploit vulnerabilities in browser plug-ins to infect computers with malware.
Php.net attack traffic captured by researchers from Barracuda Networks on Tuesday contained a Flash Player exploit, but according to researchers from Trustwave an exploit for the CVE-2013-2551 vulnerability, which affects Internet Explorer versions 6 to 10, was also used. This vulnerability was patched by Microsoft in May.
Kaspersky Lab senior security researcher Fabio Assolini said on Twitter that if successful, the exploits installed a Trojan program called Tepfer.
The Tepfer malware is designed to steal log-in credentials and configuration information from FTP client software, according to an August analysis by researchers from Fortinet.
Many users who visit the php.net website are Web developers, and they are likely to store FTP log-in credentials on their computers for the websites they maintain. Users who believe they might have been compromised as a result of this attack should probably change the log-in credentials stored in their FTP clients.