The Bugzilla bug tracker is a major part of how we accomplish our mission of openness at Mozilla. It’s a tool for coordinating among our many contributors, and a focal point for community interactions. While most information in Bugzilla is public, Bugzilla restricts access to security-sensitive information, so that only certain privileged users can access it.

It is in the same spirit of openness that we are disclosing today that someone was able to steal security-sensitive information from Bugzilla. We believe they used that information to attack Firefox users. Mozilla has conducted an investigation of this unauthorized access, and we have taken several actions to address the immediate threat. We are also making improvements to Bugzilla to ensure the security of our products, our developer community, and our users.

The account that the attacker broke into was shut down shortly after Mozilla discovered that it had been compromised. We believe that the attacker used information from Bugzilla to exploit the vulnerability we patched on August 6. We have no indication that any other information obtained by the attacker has been used against Firefox users. The version of Firefox released on August 27 fixed all of the vulnerabilities that the attacker learned about and could have used to harm Firefox users.

We are updating Bugzilla’s security practices to reduce the risk of future attacks of this type. As an immediate first step, all users with access to security-sensitive information have been required to change their passwords and use two-factor authentication. We are reducing the number of users with privileged access and limiting what each privileged user can do. In other words, we are making it harder for an attacker to break in, providing fewer opportunities to break in, and reducing the amount of information an attacker can get by breaking in.

Openness, transparency, and security are all central to the Mozilla mission. That’s why we publish security bugs once they’re no longer dangerous, and it’s why we’re writing a blog post about unauthorized access to our infrastructure. We have notified the relevant law enforcement authorities about this incident, and may take additional steps based on the results of any further investigations.

For more details, please see our FAQ document.