On Tuesday evening PST, GitHub detected unauthorized login attempts on numerous accounts, traced back to an attacker using previously compromised email addresses and passwords from other online services. Although GitHub itself was not breached, some accounts had usernames, passwords, and potentially additional personal information and repository details exposed. In response, GitHub reset passwords for all affected accounts and is notifying users individually. The company advises users to use strong passwords and enable two-factor authentication to enhance security. GitHub continues to investigate the issue, monitor for new threats, and provides updates through its blog and Twitter.