A security breach in HotCRP allowed unauthorized parties to download approximately 500 PDF files and attachments submitted to CCS 2026 prior to the submission deadline. Impacted authors have been personally contacted on January 16th. The attackers were unable to modify any submission data and did not have access to submission metadata, including author identities, reviewer identities, or review content. The vulnerability has since been fixed, and the incident is still under investigation. Further information is available at: https://hotcrp.com/news/2026/security-notice-202601