Mozilla Exposes Email Addresses of 76,000 Developers and 4,000 Password Hashes

Mozilla, the foundation behind the popular Firefox Web Browser, warned on Friday that it had mistakenly exposed information on almost 80,000 members of its Mozilla Developer Network (MDN) as a result of a botched data sanitization process.

The discovery was made in late June by one of Mozilla’s Web developers, Stormy Peters, Director of Developer Relations at Mozilla, said in a security advisory posted to the Mozilla Security Blog on Friday.

“Starting on about June 23, for a period of 30 days, a data sanitization process of the Mozilla Developer Network (MDN) site database had been failing, resulting in the accidental disclosure of MDN email addresses of about 76,000 users and encrypted passwords of about 4,000 users on a publicly accessible server,” Peters wrote.

While the data was exposed to the public, it doesn’t necessarily mean that anyone with malicious intentions had discovered it before being cleaned up, and according to Peters, Mozilla hasn’t seen any malicious activity the server, but noted they can’t rule it out.

According to a user posting a comment to Y Combinator's Hacker News who appears to be Julient Vehent, author of Mozilla's Server Side TLS and part of Mozilla's Operations Security team, the data had been downloaded only a small number of times.

"We traced back as much as we could. Access logs, netflow data, etc.," the user wrote. "We found that the tar.gz containing the DB dump had been downloaded only a small number of times. Mostly by known contributors. But we can't rule out that someone with malicious intentions got access to it."

According to Peters, the encrypted passwords were salted hashes and they by themselves cannot currently be used to authenticate with the MDN. However, Peter warned that MDN users may be at risk if they reused their original MDN passwords on other non-Mozilla websites or authentication systems. Peters further clarified in comments on the blog that the exposed passwords included salts that were unique to each user record.

Mozilla sent notices to those affected, and suggested that those who had both email and password information exposed change any similar passwords they may be using elsewhere.

In typical breach disclosure fashion, Peters explained that Mozilla was examining how the “processes and principles that are in place" could be made better to reduce the likelihood that a similar incident could happen again.