Breach date: 2014-01-09. Added to this index: 2014-09-10. Accounts affected: about 4.8M. Domain: forum.btcsec.com.
In September 2014, a large dump of nearly 5M usernames and passwords was posted to a Russian Bitcoin forum. Whilst commonly reported as 5M "Gmail passwords", the dump also contained 123k yandex.ru addresses. Whilst the origin of the breach remains unclear, the breached credentials were confirmed by multiple source as correct, albeit a number of years old.
Breach data sourced from Have I Been Pwned, used under CC BY 4.0. Additional breach metadata provided by XposedOrNot. DataExposed is an independent service and is not affiliated with or endorsed by either.
The Bitcoin Security Forum Gmail Dump breach exposed Email addresses, Passwords. About 4.8M accounts were affected.
Run the free email breach check with the address you used on that service. It will tell you whether your address appears in this dataset.
Change the password on that account and everywhere you reused it, then turn on two-factor authentication. Passwords from this breach are traded and tried automatically against other sites.