Docker says the hacker had access to this database only for a short moment, but data for approximately 190,000 users had been exposed. The company said this number is only five percent of Docker Hub's entire userbase.
It is unclear if the hacker downloaded any user data from this Docker Hub server, but if he did, he may have gained access to Docker Hub user names, hashed passwords, and Github and Bitbucket tokens used for auto-building Docker container images.
Docker is now notifying users and prompting a password reset.
"For users with autobuilds that may have been impacted, we have revoked GitHub tokens and access keys, and ask that you reconnect to your repositories and check security logs to see if any unexpected actions have taken place," Lamb said in the email the company sent customers.
While only 190,000 seems a small breach, it is not. A vast majority of Docker Hub users are employees inside large companies, who may be using their accounts to auto-build containers that they then deploy in live production environments.
A user who fails to change his account password and may have their accounts autobuilds modified to include malware.
Docker said it is still investigating the incident and will share details when available. The security incident was not disclosed on the company's website, but only via email. A copy of the full email is available here or in the image below.