On Monday, Mozilla, the developer of popular open source applications like Firefox and Thunderbird, announced that a database containing usernames and password hashes belonging to users of addons.mozilla.org had been posted publicly by accident. If you registered for an account on addons.mozilla.org and you are one of the 44,000 users who might have been affected by this accidental disclosure, you already should have received an email notification from the Mozilla security team.

Is this simply another story of data leakage in a sea of lost usernames and passwords? Not exactly. Mozilla stored passwords set before April 9th, 2009 as MD5 hashes. MD5 has cryptographic weaknesses that permit creation of the same hash from multiple strings. This permits security experts to compute all the possible hashes and determine either your password or another string that will work even if it is not your password. Mozilla did not store passwords in plain text.

The good news? Mozilla audited their logs and determined that the only person outside of Mozilla who accessed the content was the person who disclosed the accidental publication to them through their web bounty program. Mozilla has deleted the passwords of all 44,000 accounts from the addons site regardless of whether they were exposed or not.

Newly created passwords will not be vulnerable to a similar disclosure. Since April 9, 2009, Mozilla has used SHA-512 with per-user salts to store password hashes. This hashing algorithm provides a significant improvement in security for addons.mozilla.org account holders.

If you were one of the unlucky recipients of one of these emails, make sure you were not using the same password at Mozilla as you are at other sites. While Mozilla is quite confident no one other than the person who reported the incident had access to the file, if they are wrong or the discloser is not trustworthy, your other accounts may be at risk. Remember, unique password are a requirement,not a luxary.

I commend Mozilla for their response to this incident, but it does leave a few issues we need to consider. How did they accidentally publish files containing usernames and password hashes? I asked the security team and was refereed to the blog post explaining their response.

If you are a web site administrator/developer, are you still storing passwords using methods like Gawker (DES) or Mozilla (MD5)? We know they are broken and it is important to migrate away from these algorithms in case you have a database accidentally make its way outside of your organization.

Mozilla made the right decision in 2009 to begin using a much more secure system (SHA-512 with per-user salts) moving forward, but in hindsight might have prompted all of their users to migrate to the more secure hash before this incident.