Update to Security Incident [May 17, 2019]

Update (May 23, 2019): The affected 184 public network users have been notified via email.

While we continue to investigate the recent attack to Stack Overflow, here is an update on what we’re able to share today. The intrusion originated on May 5 when a build deployed to the development tier for stackoverflow.com contained a bug, which allowed an attacker to log in to our development tier as well as escalate their access on the production version of stackoverflow.com. Between May 5 and May 11, the intruder contained their activities to exploration. On May 11, the intruder made a change to our system to grant themselves a privileged access on production. This change was quickly identified and we revoked their access network-wide, began investigating the intrusion, and began taking steps to remediate the intrusion. As part of our security procedures to protect sensitive customer data, we maintain separate infrastructure and networks for clients of our Teams, Business, and Enterprise products and we have found no evidence that those systems or customer data were accessed. Our Advertising and Talent businesses were also not impacted by this intrusion. While our overall user database was not compromised, we have identified privileged web requests that the attacker made that could have returned IP address, names, or emails for a very small number of Stack Exchange users. Our team is currently reviewing these logs and will be providing appropriate notifications to any users who are impacted.

UPDATE: We can now confirm that our investigation suggests the requests in question affected approximately 250 public network users. Affected users will be notified by us.

Our team has taken, and continues to take, a number of steps as part of our response to this incident, including:

  • Terminating the unauthorized access to the system
  • Conducting an extensive and detailed audit of all logs and databases that we maintain, allowing us to trace the steps and actions that were taken
  • Remediating the original issues that allowed the unauthorized access and escalation, as well as any other potential vectors that we have found during the investigation
  • Issuing a public statement proactively
  • Engaging a third party forensics and incident response firm to assist us with both remediation and learnings
  • Taking precautionary measures such as cycling secrets, resetting company passwords, and evaluating systems and security levels

We will provide more public information after our investigation cycle concludes.