Yahoo Japan Data Breach History

This page tracks the Yahoo Japan data breach history and cybersecurity incidents affecting Yahoo Japan (Japan). BreachHistory currently indexes 1 publicly disclosed or catalogued incident spanning 2013, with approximately 22.0 million records reported as exposed across all indexed events. These totals may include overlapping datasets or third-party estimates and should not be interpreted as unique affected users.

The Yahoo Japan breach timeline includes major data breaches, cyber attacks, data leaks, credential exposures, API abuse, and other security incidents. Each incident provides details on the estimated records exposed, attack method, affected data types, and supporting public sources. Currently, 0 incidents are company-confirmed.

Largest Yahoo Japan Data Breaches

The largest indexed incidents include the 2013 — Yahoo Japan: 22 million Yahoo user IDs may have been leaked…. Record counts originating from threat actors or leak sites should be treated as estimates unless confirmed by Yahoo Japan or a regulator. Below is the list of large data breaches:

• 2013 2013 — Yahoo Japan: 22 million Yahoo user IDs may have been leaked… — about 22.0M records exposed · Catalogued incident

What Information Was Exposed?

Depending on the incident, exposed data may include email addresses, passwords, phone numbers, names, profile information, account identifiers, and other personal information (PII). The exact data varies between incidents, so review each breach page before assuming your information was affected.

Yahoo Japan Data Breach 2026

At the time of this update, no Yahoo Japan data breach has been catalogued for 2026. New incidents are added as official disclosures, regulatory filings, or credible cybersecurity reports become available.

What To Do If You Were Affected

If you believe your account may have been involved in a Yahoo Japan data breach, change any reused passwords, enable multi-factor authentication (MFA), monitor your account for suspicious activity, and be cautious of phishing emails or fake breach notifications.

This Yahoo Japan breach history is maintained by BreachHistory using public disclosures, regulatory filings, security research, and clearly labelled third-party claims. For the complete breach timeline, records exposed, incident details, and AI Breach Risk Score, explore the sections on this page.