2009 Elance — 1.3M accounts (staffing platform)
Data compromised
Usernames, email addresses, names, addresses, phone numbers, city location, password hashes
Technical writeup
Elance (now Upwork) suffered a breach in January 2009 when hackers exploited an unprotected page to access a data table. The breach was disclosed in July 2009; data resurfaced publicly in February 2017.
Root cause
Hacked - exploited unprotected page