Who this is for: members of the Yomiuri Giants' official fan club CLUB GIANTS, especially anyone who uses the same email address for other services. This article is an explainer based on the Yomiuri Giants' official announcement; it does not cover attack methods.
Developing: this article will be updated as the organisation publishes more
- Who is affected
members of the Yomiuri Giants' official fan club CLUB GIANTS, especially anyone who uses the same email address for other services.
- Confirmed so farSee the table ↓
- Occurrence
- Discovery
- Count established
3 more
- Email addresses
- Blocking the attack
- Report to the Personal Information Protection Commission
- Not yet confirmed
- Whether anything other than email addresses leaked (under investigation)
- Cause (how the access happened)
- When affected members will be contacted individually
1 more
- Whether the data has been misused
- What to do nowSee the steps ↓
- Do not open links in emails or texts in the name of the Giants or the fan club
- Check the club's individual notice before you trust it
- Review other services that use the same email address
2 more
- If you are worried, use the official contact point
- If you entered details on a linked page or got a suspicious demand, get help right away
- Where to verify (source)All sources ↓
- Yomiuri Giants, "Apology and notice about the leak of email addresses caused by a cyberattack" (November 13, 2026)
- Last checked
- As of November 15, 2026
Follow-up plans and what we checked
The club says it immediately blocked the attack, is monitoring continuously, and has not confirmed further attacks. It reported the matter to the Personal Information Protection Commission on November 13, 2026. Checking the club's notice on November 15, 2026, we found no follow-up after the announcement of November 13.
What members should do today
Do not open links in emails or texts in the name of the Giants or the fan club
The club says suspicious emails pretending to come from the club or related parties may be sent. If you receive one, do not open the URL or any attachment. If a message asks you to confirm member information or log in, open the official site or app yourself instead of following the link. For how to spot fakes, see What is phishing?.
Check the club's individual notice before you trust it
The club says it will contact members whose email addresses leaked individually, by email and other means, with an apology and notice. The announcement does not say when, or which sender address will be used.
While members are expecting an apology email, fake "apology and notice" messages are easier to slip in (our view). Before opening any link in the message, compare it with the notice of the same date on the official site.
Review other services that use the same email address
Email addresses are often used as login IDs. The announcement does not say passwords leaked. Still, if you use the same email address and password combination on other services, changing that password gives you peace of mind (our view). To check for suspicious sign-ins, see How to check for unauthorized access.
If you are worried, use the official contact point
The contact points in the announcement are the CLUB GIANTS inquiry form and the secretariat's email address. The club says replies may take some time.
Use the contact point in the official notice, not contact details written in an email or text message.
If you entered details on a linked page or got a suspicious demand, get help right away
If you entered an ID, password or card number on a page linked from a suspicious message, change the password for that service and contact your card company. In Japan you can also call the police consultation line (#9110) or the consumer hotline (188). For basic phone-side precautions, see Smartphone security basics.
What happened (from the Yomiuri Giants' announcement)
On November 13, 2026, the Yomiuri Giants posted "Apology and notice about the leak of email addresses caused by a cyberattack" on the official site. Everything below is from the club's announcement.
November 12, around 3:00 a.m.
The cyberattack began.November 12, by around 9:00 a.m.
807,030 member email addresses leaked (established later in the investigation).November 12, just after 9:30 a.m.
The system's server capacity ran short and it became inaccessible. The club investigated and confirmed that the system had been repeatedly accessed illegally from outside and that information had leaked.November 13, 1:00 p.m.
The count of leaked email addresses was established. The same day, the club reported to the Personal Information Protection Commission.
- Occurrence
- The attack began around 3:00 a.m. on November 12, 2026, and the data leaked by around 9:00 a.m. the same day
- Target
- The system managing member information for the official fan club CLUB GIANTS
- What leaked
- 807,030 member email addresses
- Not included
- Credit card information (not held in that system)
- Under investigation
- Whether any information other than email addresses leaked
- Cause
- Repeated illegal access from outside (how the intrusion happened has not been disclosed)
- Contact
- The CLUB GIANTS inquiry form and the secretariat's email address
What is known and what is not
This table is based on the club's announcement of November 13, as of November 15, 2026. When follow-up notices appear, we will update the status column.
| Item | What the announcement says | Status |
|---|---|---|
| Occurrence | The attack began around 3:00 a.m. on Nov 12 and the data leaked by around 9:00 a.m. | Confirmed (club) |
| Discovery | Just after 9:30 a.m. on Nov 12, server capacity ran short and the system became inaccessible; the investigation found the leak | Confirmed (club) |
| Count established | 807,030 email addresses, established at 1:00 p.m. on Nov 13 | Confirmed (club) |
| Email addresses | 807,030 member email addresses leaked | Confirmed (club) |
| Credit card information | Not held in that system; not subject to the leak | Not included (club) |
| Information other than email addresses | The club will keep investigating whether any leaked | Under investigation (club) |
| Blocking the attack | The cause was identified and the attack blocked immediately; no further attacks confirmed | Confirmed (club) |
| Report to the Personal Information Protection Commission | Reported on Nov 13 | Confirmed (club) |
| Route and method of intrusion | It says the system was repeatedly accessed illegally from outside, but not how | Not stated |
| Misuse | No reports of misuse so far | Not confirmed (club) |
| Individual notice to members | The club will contact affected members individually by email and other means | Planned (club) |
| Suspicious emails imitating the club | May be sent; the club urges caution | Warning (club) |
What can happen when email addresses leak
This table shows what can generally happen when email addresses leak. It does not mean these things actually happened in this incident.
| What leaked | What can generally happen | What members should do |
|---|---|---|
| Email address plus the fact of being a fan club member | Convincing emails or texts in the name of the Giants or CLUB GIANTS, such as fake renewal, fee or ticket-lottery messages | Do not open links; check on the official site or app |
| Email address | Emails imitating the "apology and notice", leading to fake sites that ask for logins or card numbers | Check the club's individual notice against the notice on the official site |
| Email address (often used as a login ID) | Login attempts on other services where the same password is reused | Change any reused password |
What is reported to have leaked
- Member email addresses (807,030)
- Anything other than email addresses is under investigation by the club
What the announcement says is outside the scope
- Credit card information (not held in that system)
- No misuse has been reported so far
Sources (public record)
The facts in this article are based on the official announcement below. We do not speculate about causes that have not been disclosed.
- Yomiuri Giants, "Apology and notice about the leak of email addresses caused by a cyberattack" (November 13, 2026) — giants.jp (in Japanese)
Update history
2026-11-15: First report, based on the Yomiuri Giants' announcement of November 13. We checked the official notice the same day and found no follow-up.
Read next
- A case where electronic ticket member data leaked: The teket incident
- How to spot fake contact: What is phishing? / Smartphone security basics
- Suspicious activity on an account: How to check for unauthorized access
- Other incidents in 2026: Data breaches and cyberattacks (Japan and overseas)